Made more progress at getting the bike back together, also had delivery of more stainless bolts.
Fitted the rear tank back on, but had issues with the tank breather tube being split and its a really tight fit plus the threads in the frame required cleaning with a M8 tap.
Whilst refitting the rear light and number plate assembly I noticed the rear light cable had been pinched by the cable guide, so will need to shrink tube over the top as the copper core is exposed.
Replaced stacks of bolts with stainless ones, fitted the new number plate light and rear mudguard. I swapped out the chain adjust screws for stainless nuts and bolts – M8 x 55mm.
I then discovered the lower chain guide block is distorted, I managed to straighten it using a plastic mallet, but the aluminium is so soft it will happen again so will be swapping it out for an Acerbis one from rugged roads
One thing to note is from the state of the original rear tank is the moulding holds water and will cause corrosion of all the bolts, so make sure you remove it and grease all the bolts before its too late.