Cancelling IFR should be used with caution. A contact or visual approach can be requested by the pilot, whilst remaining on an IFR flight plan.
I read an interesting article in the AOPA magazine a while back, admittidely the US one, so some of what was said will not apply in the UK. But the gist was that an approach controller under heavy workload was "encouraging" pilots to cancel IFR as soon as they were visual. None of the commercial operators in the queue did, but this PPL decided he'd help the controller out and cancelled when he was visual. He was met by an FAA inspector on the ground, who wanted to know why he was flying VFR in less than VFR minima (for the class of airspace that this airport was located in). The pilot was "prosecuted" by the FAA..........
EA