I would be tempted to inspect the wiring first, both underbonnet pump and in tank pump are wired in parallel, and it would be a first to find a pump causing the fuse to blow.
It's so rare, I've not come across a pump ever to cause an overcurrent trip of a fuse, it has always been the result of chaffed wiring, if you suspect the in tank pump, then simply disconnect the supply to the pump temporarily, the +ve supply being the white wire with purple trace.
Brian
