If you have had an FAA IPC within the past 2 years, plus a UK/JAA PPL and medical etc, then you can apply for an IMC Rating.
The CAA disregards the FAA IR rolling currency, which is why a current IPC is required.
Then one can fly IFR in Class D also, UK airspace only.
The IMCR minima are the same as the full IR. The "higher minima" are a recommendation, not law.