lift pump can be bought from GSF for ?20 and fitted in about 30mins
the lift pump sits within the tanks. it takes the strain of the main pump. to get at it. you need to lift the boot carpet then undo the 3 screws on the back plastic cover. then disconnect the fuel lines and then undo the big black plastic ring. this is really usually really stiff, you'll need a hammer & drift to undo it
remember the orientation of the pump when you go to take it out!!
lift the whole lot out of the tank and then you'll see the little motor that you need to replace.
when its out. its worthwhile give the little strainer on the end of it a clean also.
your main fuel pump might just be a noisy pump. my current one is noisey as fook but still provides correct pressure