If you carry at least 40litres in jerries/aux tank, then even a destroyed main tank will not strand you. There's some maths involved in this, but basically whatever you have left should get you where you wanted to go or back to where you filled up, or at least near enough!
(This is presuming you have the 80l rear tank, 20% total contingency and obviously you only need to do this where fuel stops are few and far between.)
Bring enough plastic tubing to connect a jerry to your fuel line and clamps to seal any redundant tubing to the damaged tank -- this is all easy to do and stuff that's useful to carry in any case. Any bush mechanic should be able to patch your tank or bodge in some sort of replacement.
There you go: rare worst case scenario catered for and £300 and ??kilos saved!!!
EDIT: Being of feeble brain this morning, I've approximated the maths here somewhat, maybe someone can add to this!!