I have what sounds like a big end rattle on startup from cold only, the rest of the time it's fine. it doesn't rattle when i bring the revs up gradually in neatural and doesn't rattle under load, also there is no rattle on startup when warmed up.

I know the oil pressure is good, i've checked it with a workshop pressure tester

Any ideas

lifters ??? the boys that know will be along shortly

Try lifter lube from halfords, works for me. most of the time.