Firstly thanks everyone for such prompt and comprehensive responses.
Working through the points made, the car has done just on 200k km so I took a punt that the head was unlikely to have been off too many times and so i reused the head bolts. And it is all a bit caught up in the situation of just trying to get the car home - it is about 250km SE from where i live in Adelaide on the inlaws farm. I had been doing work further south and then broke down only about 15km from the farm, so rather than explore more costly options of moving the car, my father inlaw just towed me back to the farm so i could explore the options and was heading to Adelaide that day anyway, so i caught a lift.
What happened was the plastic clip above the water pump that holds the heater hose broke, heater hose rubbed on the pulley and next thing i am overheated. I let it cool and had water on me but didn't realise about the hole until later. It started and ran perfectly but a few km down the road overheated again. Then i turned it over without that brass screw in place on top of thermostat and it belched water out. I don't even know if that is normal but it was enough for me to suspect the gasket and hence the tow. Since then someone suggested a few things to try apart from gasket, but at 200k i have heard suggestions it is not a bad practice to change it anyway.
Because i was pretty sure the overheating wasn't too bad or too long I decide to take a punt and change it and see what happens - only a $50 gasket, few other bits and a bit of time vs something like $300 to get it transported here to then deal with it. And there was a family get together this weekend we were attending anyway at the farm - long weekend public holiday for the Queen's Birthday - I know when i worked in the UK (Worcestershire Wildlife Trust) my colleagues found that humorous! So my kids and cousins played, Wife caught up with family and i was perched up on the defender working, that the odd spectator that visited the shed over the weekend seemed to find very funny!
But back to the bolt subject, I can see all the points that have been made, I can see logic in all of it. Some more info, i checked the head with a straight edge and was pretty good but not perfect and combined with a bit of corrosion where it meets those triangular water holes - well in a perfect world i would have had it faced but that would have involved another 500km driving. I also noticed a bit of wear in those brass cam follower parts, bit of scoring on no.4 cylinder and noticed while a standard bore piston still, the brand was different for that one - so no doubt a past dodgy repair.
But what started as an experiment with this Defender (see my intro post i will do) I am a total convert now and it is perfect for my needs. So if i can get another year or so out of this engine that would be great and the gearbox, and then I will fully rebuild both. Long story but i have a very rusty 200tdi that i am 'derusting' and will sell eventually but will use that while i am rebuilding the 300tdi - bore, oversize pistons, new head studs and new head i would think - and one of those temperature alarms!
So, given that long winded background and all the info, i think i will take a punt and just do the two, save me redoing all the valves, but will check - but mainly i am thinking that someone has done it and been ok. If it all goes wrong, if the head is not straight enough etc etc, then it can all still go on a truck back to Adelaide and bring the rebuild on sooner. I can see the point to slacken all because the crushable parts of the gasket have not perhaps settled properly yet and letting it go disproportionately could crush different bits. But i am thinking of all those bonding bits on the elring gasket that i scraped off the head and block and i imagine that is not ideal for that to lose contact and more likely if i back it all off. If i was about to head off through the Simpson Desert then I would pull it off, get a new gasket and start again.
I'm thinking I might see if i can pull one bolt, put it back through one hole in the bracket, put a degree of tension on it and then see if i can swing in to put the last bolt through while it has some tension back on it - just a thought so it doesn't lose all the tension at once. I had to come back to Adelaide without the car last night, but will be back down again soon and managed to break the dipstick tube and that would be good to get a new one of them. Will give the air cleaner thing a bit of thought to. I found it unusual to have that bracket under head studs and also the water pipe under exhaust manifold nuts. Part of even pressure and getting tension even i always thought had something to to with friction against the nut or bolt face and having different materials, steel and alloy and cast - but what do i know! Obviously isnt a big deal since these cars have done billion of miles.
Anyway, thanks again. Will report back when i try to start it.
