boiler pump

I had a new Worcester Bosch 28CDi boiler fitted in my flat recently. It works, but I've noticed a strange thing. Sometimes the gentle humming sound from (what I assume is) the pump fluctuates - the pitch rises and falls every 5 seconds or so. Is this normal? It's quite distracting (sounds like...

Recently my oil tank ran out of oil and when I got the tank refilled the boiler wouldn't start so my landlord sent around a plumber who supplied and installed a new oil pump and bleed oil to fix the issue. My landlord is now giving me a bill for £145.32, I have 2 questions 1. Can running out of...