The Cambridge Latin course is very easy and accessible, and doable without a tutor - just beware that if you want to continue to A level, or higher, the Cambridge course is not a good basis for that as the grammar is very patchy - in some places I have noted it is actually wrong. This so doesn't matter for the purposes of GCSE (which is very easy compared to other subjects, and only requires an elementary grasp of simple grammar, and certainly is much easier than MFL GCSEs) but can be a shock if the student wants to pursue it at a higher level. If the student is serious, it would be better to get a tutor. (btw, am not a tutor, and not touting for business for tutors )
I second SD's comment about the sketchy grammar content of the Cambridge Latin course. I did this one myself back in the day - the first year's worth of which I finished over a summer holiday, did the rest over the normal course of a school career, got an A in the O-level, then on the strength of that decided to take it to A-level. Ouch. I had a lot to catch up on. Fortunately, my teacher was well aware of the problem and gave me extra sessions to rectify the gaps in my knowledge.
I was chuffed to end up with an A at A-level as well, but didn't do Classics as I decided there was more to life than the private life of the gerund.
When I was doing Cambridge Latin course in the late 80s, we had some additional grammar workbooks to go with it which were great. I really don't know whether they were widely available or just something the (small!) group of local teachers had put together (this was in Australia).