Looks like it's time for you to get in there and have a go yourself. Otherwise its going to cost you a fortune and you're going to get ripped off, by the look of it.
You don't want to let her go.........so don't, have a go, you've not got a lot to lose and you might be amazingly gratified in fixing it yourself at minimal cost.
First thing I would do is disconnect the fuel supply line to the fuel pump. There is a small strainer in there. Its the first line of defense from crud in the tank. I'll put money on that being full of corrosion deposits etc.
Not sure on the exact procedure for cleaning out the tank but I would imagine it would need to be removed. Removal is not too difficult, can't be as I've managed it.
If I lived near Bath I would willingly come and help.........unfortunately I don't, but I and plenty of others here will willingly advise if it help you to keep the car.