You can also use the Jeppessen CR circular types if you wish. They have all the scales required for the exams. Some types of problems require fewer steps to solve compared to using the CRP slide type computer.
I've been using them since '87 & much prefer them to slides. I, and a number of others used ours when we converted from our Oz or NZ licences. The catch is that few instructors in the UK are willing to become familiar with the type although it's not difficult - the small manual that's supplied is quite sufficient. That's all most of us who use them used.
They're also a lot cheaper at ~US$25-30.00.