Haven't had a chance to do anything else to it just yet. New PAS reservoir has arrived (the old one leaks from a join), along with oil and filters (incl fuel filter).
Monday I'll be having a chat with my local mechanic (who luckily is an excellent welder!) armed with various photos, and then hopefully it should be going in to him to inspect properly and give me a ball-park figure for the rot repairs (only the ones to the shell for now.)
Filled it up again having driven like a bit of a loon on the last tank, and mostly town driving at that. 21.7MPG. Pretty pleased with that, was expecting high teens!
It does feel strange to look at the numbers "21.732" on the calculator having worked out the MPG, and to be pleased rather than shocked!