Coolant problems again.

Been almost a year since i last done my headgasket and its possible that its going to need done again but first I thought id ask you guys and tell you symtoms first to see what you think.
About 3 weeks ago we had a nice warm day after the car had been driven fine for 2 hours it was left sitting for an hour upon getting back in the car noticed no heat from heaters. Temp guage had only just came upto temp. Pulled over to check coolant lever but couldnt undo the cap as there was a load of pressure and coolant would just run out. Dicided to move car off dangerous part of road and as i was driving temp guage rised slowly but not all the way to red, then dropped suddenly and heat came back through. I though it was a airlock that had cleared all seamed fine after that until yesterday. Again warm day temp into double figures and lost heat through matrix and temp guage shot up managed to keep rolling slowly and got temp back down. Eventually shut engine off to check coolant, masive amount of pressure in reserviour so undone rad plug and it hissed out there. The rad and thermostate housing had no water in it whatsoever. Filled from thermostate housing and bleed from there too all air seamed to escape as it should once ran on full throttle for a period of time the upper and lower rad hoses go solid but doesnt seam to cause coolant to come out tank when releasing cap, i do get a return feed into expansion tank of coolant and exhust doesnt seam to be bubbling back through the bottle. Drove it to work and back today heaters ran fine and temp sat half way hoses still solid though.
My rad is missing alot of fins but not all. Second hand one on its way with one of the electric fans fitted. Notice there is mixed feelings on them.
Anyone had problems like mine and could say what it was, i feel its heading to another HG fit but would like to hear you guys thoughts.
Thanks

Should of said its a 300tdi

To confirm a leaking head gasket or not, park the vehicle nose uphill with engine cold or warmed, (not hot, danger), remove the bleed plug carefully from the top of thermostat housing, that is the highest point on the cooling system, also loosen the cap on the coolant header, pour in coolant where the plug is removed from until the system appears full, and coolant runs out from the loosened coolant tank cap, tighten the cap, start the engine and let it idle whilst observing what is happening at the open bleed point, the coolant may initially drop as any air locks are expelled from the system, or some may overboard, keep it topped up and watch for tiny air bubbles or foaming at the bleed port.
If you observe bubbling/foam then that will confirm air/combustion gasses are leaking into the system.
You say the hoses go hard when running at road speeds, this could be an indication that the system is over pressurising from the ingress of combustion gasses way above the normal 15psi that the cooling system works at when the temperature is up. Usually even on a pretty hot engine the hoses can be squeezed.
The presence of air in the system plays havoc with the temp gauge sender as it is tin that thermostat housing and needs contact with coolant to register, the air rises to the highest point in the system that can explain crazy gauge indications.

When bleeding intially there was foam and bubbles from bleed screw that stopped after running it at full throttle for a while and looked to expell all or most of the air on the run home after everything ran as it should with exception to hard hoses. Could a airlock cause a build up of pressure. The last time i had problems i had a crack between 2 piston seats on the head, you coulf see the water bubble as exhaust gasses came out expansion tank or does this not always happen and just depends where the fail is?Also i know the cap releases air when pressure gets to certain point but does it constantly leak air on a normal working system ei. If my cap was faulty its allowing to pressurise to much and has maybe gone through next weakest point being th HG.

Head gasket leaks can be miniscule, so the passage of combustion gasses (very high pressure), into the coolant can take a while and in normal terms be nearly undetectable, but given the number of times per minute (engine RPM), that miniscule amount of air is pushed into the coolant galleries as it is of such high pressure when released into the lower pressure of the cooling system, it massively expands thus displacing the corresponding volume of coolant, which has to go somewhere, i.e. the point of least resistance, the pressure cap. It is not uncommon for there to be no coolant getting back to the offending cylinder until very late stages of the failure, engine performance can be still ok until the leak gets to a bad stage.
The pressure cap on a normally operating system is generally not meant to leak at all, it has to maintain the system pressure, increased pressure = higher boiling point, so unless your system is boiling or there is higher pressure being introduced into it, the cap should not leak. In my Tdi I can sometimes hear the system sucking a little air back in after shutdown as the system cools and contracts, the Pressure cap has two one way valves, one for out set at or about 15psi for relief and an in valve that opens under atmospheric pressure to put that little bit of air back into the tank to work against to maintain the pressure next time you start up.
As I said the hard hoses could be caused by pressure ingress, and the system has a little expansion room capacity in it to accommodate pressure fluctuations so how "normal" it will be will depend on trip duration, short trip maybe can cope, over long run it discharges coolant and air pockets sections of the cooling system.
To test maybe, next longer run top up the system to your total satisfaction, do the run, then after engine has cooled again check level, level lost will indicate coolant discharged (leakage somewhere).
An airlock can cause little "micro-boil" pockets within the head galleries and that will of course pressurise the system as those pockets of steam flash off and expand, but the problem should not continue in a properly filled and bled cooling system, only the continuing introduction of air into the system somewhere keeps those pockets occurring.

This sounds very familiar

You didn't mention the lovely Rac Patrol who came to your aid

Not to forget the lovely RAC lady that saved the day and got me going again. Plus had a good chat about landies.