Fuel Pump

[TotalControl]

Need a bit of help guys. Need to change the fuel pump on my mums 318 4 door(y reg E46 i believe) as the car sometimes doesn't start or when it does, can't idle properly and cuts out. Am i right in thinking that the fuel pump is not adjoined to the fuel tank of this model? (That would save me having to replace the fuel tank, i think). Its just that I need it replacing quickly but i need to buy the part and hand it over for the replacement. Have tried to google for it but to no success. Any links would be grateful. Thanks in advance guys.

[TotalControl]

Well, sometimes the car starts absolutely fine. At other times it tries to idle but fails by being erratic then choking. If i start it up and put my foot on the accellerator it just dies and doesn't start. It seems to start fine when cool though.