I think you may find the fuel pump for the FBH is located on the chassis just in front of the vehicle fuel tank.

Cheers
Col

UPDATE

Well almost a year later and i still havnt got round to fixing the FBH....

i have checked it again and the burning smell is actually coming from large plug in the top of the heater - smells electrical to be honest....so i am thinking the circuit board might be fried - need to check the usual things like if the pump is supplying fuel first and the water pump is working - if so i can pretty much decide its the board and will just buy a replacement heater...which looks easy enough to swap out in a couple of hours...

trust me to leave it until the temp starts dropping again!