Hi, you don't say what car you have but i presume its a lift pump (since hitting the pump/ tank is mentioned), it depends ion the car but you could probably aqquire a new (pattern/ oem )pump for about £100 (locally or online) and get it fitted for about the same again, the £400 seems like main dealer prices/ genuine Ford for a lift pump (but of course i don't know which car you have so these figures may not be accurate)

People expect cars to be 100% reliable, you could spend the £400 and it could still keep breaking down all the time (there are 1000s of other things to go wrong!), or spend/do nothing and the car keeps running!

it may work uot cheaper to get premium "get you home insurance"/ extended AA/ RAC covarage, to put your mind at rest, not a bad thing to have anyway and worth investigating