hoping it was faulty? but on tick over the oil light flickers very dimly when its up to temperature, but as you rev the engine it goes out, there's no rattles from the engine and it uses no oil.

Hi
If youve replaced the oil pressure switch with a new one you have an oil pressure problem!
This can be caused by several things but the most likeley is either the oil pump or low viscoucity oil.
Try replacing the oil first with a good quality castrol/shell 15/40.
If this doesn't fix it then you need to strip the engine to get the oil pressure pump replaced!
It could also be a sign that there is excessive wear within the engine big ends,little ends or a blockage in the oil feed to the pressure switch! HOPE THIS HELPS!