Whizzwheels
Gazman21
For your JAA ATPL groundschool definitely stick to the CRP-5 and no other, crude and overpriced though it is. (CRP-1 is no use at ATPL level as it doesn't provide for MACH and density altitude calculations).
It is quite true that UK/JAA instructors are often familiar with only that one device and, surprise, surprise, the JAA examiners only use that one also.
If you get another type and you get into difficulty in class and you have to call the instructor over to help you he/she will be well brassed off if he/she has to keep the rest of the class waiting while he/she figures out the differences between your whizzwheel and the one everybody else is using.
There are indeed several other makes of whizz on the market, but remember you are doing the European exams and some of the problems you will have to handle involve conversions between, say US gallons, Imperial gallons and litres. Some of the American whizzwheels don't have all of these options, and may lack especially the metric measures.
Finally, when you get the whizz, get a small screwdriver and strip it. Rub the bearing surfaces lightly with a piece of wax candle. You will then find it will run more smoothly and will be less likely to jerk past the point you are aiming for when you are trying to work quickly. The General Nav exam has a reputation for being a race against time, so even seconds saved when you have nervous, fumbling fingers is worthwhile. (Actually, I took the General Nav exam twice and found it OK as regards time available, but then I always liked Nav whereas many don't).
Good luck with your ATPLs!
Broomstick