seems that this winter might be a good time for a fuel tank, breather and filler neck replacement. my gauge was o.k but the sender was shot. i had a new alternator conversion, carb and inlet manifold waiting to fit so when i took the engine out i drained and removed the fuel tank, cleaned inside (43 years old and it was almost like new inside!), flatted and painted outside, flatted and painted the tank space and bulkhead and all engine tinware, replaced all breather hoses with 100 percent biofuel hose and replaced the filler neck with a new one (not very good but the only one available), replaced sender with a new VDO one at a cost of £70. should be good for years to come now!
Well worth doing, not as big a job as it seems if you are removing the engine anyway. if you are gonna do the biofuel hose though i would sit down before you look at the prices! to keep prices down, measure how much you need exactly of each size before ordering. i also replaced most of my fuel supply hose with 6mm stainless pipe i fabricated to fit so will only need a foot or so of hose in future as the stainless will last forever!
good luck with it all.
cheers, dave.