I reckon Jellycopter is correct.
Unpalatable as it may seem to some, UK IFR rules do allow this in Class G airspace.
However, the relevant part of Rule 5 (i.e. 1000 ft rule) must obviously be complied with.
I don't see how Crab can relate an IMC approach in isolation to folk allegedly relying on the so-called "Big sky theory".
If an aircraft is being operated in the descent to land whilst IMC without radar cover (or other means of being made aware of others, such as TCAS), it is no different from doing the same in cruise flight under IFR, with respect to aircraft separation, which is also allowed under UK's IFR rules.