Hello.
Just a quick update on how it went. Its been three months but that's because we've had other things to sort out house, job and work wise.
So, we got the gasket replaced with the odd hours here and there gradually over the last three months. Its been an excellent learning curve. Confident of doing another HG replacement in future (although God forbid not needed!)
It looks lke the main leak was at the back right of the head - and funnily enough the CH bolt at that back corner was the easiest to undo with the bar so was probably not torqued up in the first place I guess.
Since buttoning it all back up two weeks ago, it has since done over two hundred miles without any loss of coolant or oil. Coolant smells as it should and oil looks as it should.
Took the opportunity to clear out all the breather pipes, idle valve and also tested the thermostat. All good.
It is running fine. Takes about 10 mins to get up to 85 degrees then temp fluctuates between 85 on straight runs and 88-90 if stuck in traffic so all good. No back pressure and water loss from expansion tank like there was previously. No white steam whatsoever out of the exhaust. Touch wood she'll be good for ages now.
Washed the car whilst it rained this morning.
I'll post some pics later today of what we took whilst doing it.
Thank you again for all your messages and help offers.