Did he test the voltage at the fuel pump? What condition is the tank in? At the very least i would change the fuel filter. fresh fuel and run it through the lines and check to see what the inside of the tank is like. Just need to disconnect the hall sender while you pump the fuel through.
Unless the wrong pump has been attached i am not sure what could have happened to the current one. If you cant get a good used one. Syntec do a decent one for circa £50 (iirc)
Let us know how you get one, couple of pictures may help
Also welcome