the humming noise is not coming from the burner but from the heating system.. it sounds louder when i stand beside the exhaust vent at the rear of the unit
It's probably a priest you need so, lol!!!
Your Hi-Limit stat will not be located in your Hot Press this is more likely your cylinder stat.
The Hi-Limit stat is located on the boiler( as opposed to the Burner) itself, and is normally a Grey or Orange box with a dial and a small cover screw.
If you can locate it remove the small black cover and press the concealed button below.
If this doesn't work your best bet is make that call.....
Sorry but you are clearly lost with this problem and have no clue of even the simplest things on your system, i really would suggest you get your local oftec tech in to have a look rather than us start to explain how to open this and that and test for live cables, i really wouldnt like to see the priest have to call.
For us to guide you, you really do need to already have some basic knowledge
found the boiler hi limit stat but there is no black covered screw only the dial.. and yes lad i have not got a clue about the system whatsoever but cheers for the help anyway.. will post the results when the priest calls ..
is it like this
the black knob unscrews to reveal a button that needs to be pushed firmly in to reset