In answer to questions, the engine doesn't stall when idling in neutral or in drive when stationary only when applying a small amount of revs when starting to move; engine rpm drops off suddenly when the power cuts out; no aftermarket BOV is fitted; idle rpm in neutral with handbrake and no a/c is 750rpm, with a/c on start up goes to 900rpm then drops to 800rpm.
Sunday is my only day off work so will try and do the checks suggested then.