Removed the tank from my car recently and the base was rotten to no surprise, but the rest of the tank was in excellent condition.
A friend recommended a local company that specialises in all aspects of welding and metal fabrication, the tank was dropped off a few weeks ago and the chap said subject to checking the insides for corrosion he could cut the rusty area out on the base, fabricate a new section and tig weld it in.
I picked it up yesterday and I can only say what a smart job he has made of it and fluid tested it too, and the bonus, it’s rot free inside, so I’m assuming it’s perfectly acceptable to repair a tank.
If anyone’s interested in getting theirs repaired I can pass details on, he’s in West Sussex.
I did pot the question about fabricating a new tank from aluminium to the same shape/dimensions which he can do and estimates £350.