Also have a look at the Scales of Equipment in the ANO which will have a list of the minimum equipment you will need (two altimeters and FM immune radios etc for the IR)
If you want to do your IR in your own aircraft you will also need to have instrument screens made - it is possible to get them made so they don't damage the combing in the aircraft but are a bit of a fiddle to allow the P2 side to have a good enough view.
It may be a little pricey but, then again, you may find that your course durations can be closer to the minimums because you are flying an aircraft which is so much more familiar.
Good luck!