Boudreaux
I am not in the UK.
I was not really intending to refer to # of engines pre se but single engine helicopters are usually mostly VFR equipped with VFR rated pilots so IIMC at night and the system which allows night flight in lesser equipped helicopters is, in my opinion, in need of tightening up.
However, your point is well taken that the UK currently has an appalling IFR twin engine fatal accident record, the A109, the EC135, the 332L2 and now the 139 all in just over 12 months. Moreover, they are all human factor and decision related to one degree or another.