I'd have to agree with FISH.
If you need 25 hours you can get 5 completing your night rating and the rest flying round the UK either at night or at day getting used to the airspace and RT.
Most IMC pilots will tell you that it's the one rating you need to keep practising else you'll quickly lose the knack. The best place to practice is on your local procedure which you will have done 30 or so times before during your training. Obviously if you do your IMC at NAC that is no longer an option. You have to be careful that having completed the IMC at NAC you don't find yourself in an uneasy situation if you come back to the UK, get yourself into IMC in an area where you are not familiar, with radio procedures that are different from what you are used to. It just all adds to the pressure.
As far as aircraft goes, it doesn't really matter as long as they've all got enough instruments and Nav Aids. Go for the aircraft that you are most comfortable flying.