Cheers man,

Yep, ex uk car here as well. I have done some research since my original post and it looks like the tank just needs to be unbolted and shifted as opposed to removed altogether, was this your experience ??

My car has a lot of fairly ugly looking surface rust, at least it did till I attacked it with a wire brush, but, not rotten through thankfully. It was on the list of things to do but is now number one priority.