15 hours at £150 per hour is well out of reach of the average UK IMCR holder who does not have any need for full IR privileges.
By the time you add travel and subsistence, plus a test with a CAA Staff Examiner, I can't see there being any change out of £3000.....
When I did my first military Preliminary Instrument Flying Grading, I had all of 12 hours TOTAL IF time. The test involved full and partial panel flying, plus an 'ACR7' surveillance radar approach into RAF Andover in a Chipmunk with a floor mounted compass!
Why this CAA/JAA/EASA obsession with total training time?
Even when I flew the Gnat, I only did 6 hours IF in it before taking the IRT (which was VERY demanding! I was utterly amazed that I'd passed). I had to do a navigation exercise to Pershore at around 350KIAS, a TAC/ILS approach then back to Valley for a QGH to GCA, touch and go then a short pattern GCA to land. Total 1:10, of which 1:05 was IF - with all of 6 hrs IF time on the aeroplane plus another hour in the primitive simulator.
I can say from a background of IF in everything from that Chipmunk to being a VC10 IRE, with IRs on various military fighter, trainer, bomber and transport aircraft as well as being a strong advocate of the UK IMCR that the UK IMCR most certainly gives the average GA/PPL holder (except for those who wish to fly long distances on airways) everything he/she really needs for safe IMC flight. Fortunately, many of the more senior people in the CAA agree with me.