Another vote in favour of Cranfield ATC, if they need it.
I've been based there for many years as a private owner, and have heard each of the ATC team there at different times dealing with some quite incredible stupidity from various pilots both visiting and home-brewed.
I have never come across any situation there in which there has been any uncertainty at all about whether an arrival is under IFR or VFR. Where such doubt exists, the onus is in any case on the pilot to specify the type of clearance required if he either doesn't wish to, or cannot comply with the clearance he has been given.