Freelander '04 TD4 Fuel Pump, filter, sedimenter and ???

Hi, just changed the wheelarch filter and pump. Disappointed that the new pump (from Ebay) is REALLY loud, and hearing the odd air bubble go through even though I've done a few miles. Anyway, I didn't know what the extra device was, as in the photo. Any ideas? It's a standard part, but extra to the pump, filter and sedimenter.
Thanks!

That must be the fuel burner heater fuel pump

Ah yes! I'd forgotten that would have it's own pump. Thanks!

Advice on here would have said get the oem bosch LP pump

Thanks, yea - I know, probably a false economy, but as it turns out the fault I'm trying to fix (surging/pulsing every second or so at tickover or whilst driving) didn't make any difference so at least I've not wasted the £120+. Next to change in order:
Fuel rail pressure sensor and harness
Maf/p sensor
Injectors
Injector return pipes
Cam/crank sensor
Anything else or different order? EGR all cleaned out the other day and fault unchanged. Pulsing/hesitation very noticeable on tickover (no load) after blipping the throttle.