A Jepp CR was quite ok for the UK national exams. I and a bunch of others used CRs for our British ATPLs in 1999 ie prior to JAR. We found that they were faster to solve some problems and more accurate overall. Our spread of answers were nearly always a tighter cluster around the correct answer compared to CRPs. Considering mine is a CR5 (the smallest at 3 3/4" and therefore the least accurate) I still did better than many CRPs, I have to wonder at the death grip CRPs have on the market in the UK.
I've been using mine since 1987 for Oz IR, Oz ATPL, FAA ATP & UK ATPL and god knows how many flights across the outback & North Sea between Shetland & Scotland. Damned if I'd want to go back to a slide type - and my slide E6B is a Kane, one of the better ones that used to be on the market (no good for high speed stuff though).