Update:

My dad and I took a wire direct off the battery to the red and black wire and manged to get the fuel pump to work. We've since reconnected the battery, put back all the trim and the fuel pump now works, with a bit of wiggling of the wires. I can now drive the car to the garage, and they'll be lowering the petrol tank and checking/changing the wiring on the fuel pump itself.

Thanks for your help 3drstretch.

Hopefully be totally sorted this week. Hooray!!!