WRT to the UK JAR exams I borrowed a CRP5. For work I use a small jeppesen style whizz wheel.
The smaller one is a lot easier to use in a real world situation whereas the CRP 5 would be cumbersome. I used a CRP1 for my initial navs in Australia and I found in a small cockpit it's just a bit big to use easily. I find it's far easier to slot the jep style whizz wheel into my pocket and as opposed to having to rummage around a nav bag when the instructor gives you that inevitable diversion.
Actually, that's probably the one major difference I have noted with the pilots in the UK. The Aussies have their little jep whizz wheels in their pockets, the Brits have their CRP somewhere in their nav bag.
If you're really cluey you'll check eBay UK for deals. Try "Pooley flight computer" in "All categories" and you might be lucky.
