I'm in a similar position and asked the same sort of question back in June. Here's the link to the thread:
http://www.pprune.org/forums/showthread.php?t=231827
Incidentally, after weighing it up, I think I'm going to start the IMC quite soon as it's clearly more constructive hour building than anything else I could do before getting to 150hrs. Plus, it's not drastically more expensive than flying solo at a club, say £30/hour extra, for 15 hours, that's £450 and a bit more for the exams and our friends at the caa (£100?). Then with the rating, you might save some money on the IR when you really start spending. My opinion anyway!
All the best