The IMC rating previously was just a get out of trouble rating, a good grounding in Applied Instument Flying. However as it gave no ability to fly IFR in Special Rules Areas B which comprised the major airports which had radar and an ILS, it was of no value in planning to fly cross country IFR unless there was a reasonable chance of a visual approach at the other end. I think the only ILS which was available in IMC was at Stornoway.
The change came when IFR was permitted in the Class D airspace into which the SRZs had changed. Thus it was now possible to fly across the country IFR and make approaches, all with no Flight Plan and no fuss, as long as one remained clear of Class A. I appreciate the continuing informality of UK cross country IFR but I also think that the real answer is an easier to achieve and maintain IR and await the next text from FCL 008 with interest.