Code Blue
Yes - VFR in the United Kingdom does require you to remain clear of cloud. However, there is no problem with switching between VFR and IFR outside of controlled airspace without filing a flight plan (indeed, you don't even have to be talking to an ATC unit) providing you comply with the Instrument Flight Rules and, if the flight involves flight in IMC, you are qualified to do so.
Practice instrument approaches in the UK do not require the flight to be conducted IFR, and so no flight plan needs to be filed. However, if the student pilot is flying under the hood then the instructor or safety pilot must have unrestricted views outside as well as full access to the aircraft controls. If he does not have full vision (possibly due to blind spots) then another observer must be carried to cover any blind spots.
As for the accident statistics. Yes, inadvertant flight in IMC (and I think it's important to differentiate between IMC and IFR here) does tend to result in a 'smoking hole'. Anyone unqualified who does it is asking for an accident.
CM
[ 23 November 2001: Message edited by: Chilli Monster ]