A couple of weeks ago my P reg 300tdi discovery overheated on the motorway. Coolant pressurised and sprayed out of the header tank.
I removed the head and sent it off for checking.
I couldn't find any sign of a break in the head gasket.
Head came back as warped so was skimmed and sent back to me with a head saver shim as it was skimmed "beyond manufacturers guidelines".
I put it all back together with an elring 3 hole gasket, new head set and new thermostat and temp sensors.
Bled fuel and coolant up, started after a couple of turns and seems to run fine. Been out on a 10 mile drive, no signs of overheating but when I stopped I had a massive air lock. Header tank was pressurised. I re bled the system thinking there must have been a lock lower down the engine.
I have since bled the system more times than I care to mention.
Temp sensor remains bang in the middle of the guage, no water in the oil and heater blows hot. If I bleed the coolant without driving it bleeds up fine until I drive then it pressurises. All I can imagine is either the head is knackered and wasnt checked correctly or the gasket is faulty which I think is less likely.
I have rang the firm who skimmed the head who said they would re check it, however, I doubt they'd admit if there was a problem or claim it'd happened since fitting (about 20 miles ago).
Do I buy a recon head or go the whole hog and look at getting another engine in case it's an issue in the block (which I believe is very rare).
Any body else had this problem and what was the solution. I have ruled out any blockages or air locks. Since replacing teh head gasket it also struggles to start from cold. Any advice greatly received.
Thanks.

As James Martin would say is the rad getting hot all over and not short cycling -also is water pump pumping

Yeah. rad is hot all over. Water pump was new 200 miles ago when it had a timing belt.

head gaskets arent allways blown through ,its staining around fire ring ,water ways etc you are looking for ,if head was that bent it was buggered once aliminum head has been so hot the internal stresses are lost and it will move again once warmer enough,any firm skimming heads should know that and warn you its chancey,new head err5027 £260 if after removal its not flat,rad does need checking allover as is biggest cause of head gasket ,but yours is old enough to go anyway just on number of heating cycles,you should regulary check level with both bungs removed expansion tank level is no indicator of engine level