Hi. I didn't attend any course for the UKCAT and did very well. I think it's just a case of going through the questions and understanding the concepts. The more you do, the better you become and there are so many sources with decent explanations. Going to a course for the exam may help if you don't understand the questions (which I don't think is that common), and from speaking to people it boosts your self-confidence.
For me, I felt that the quality of my personal statement was not very good, and I am not very confident with interviews at all! I signed up with "UKMeducation" and I found them useful, especially for their personal statement analysis and interview coaching.
I think that much of it can be done on your own, especially the exam parts. A bit of help is always nice, but if you are going to pay for something like courses/tutoring don't just do it for the sake of it, but see what you can gain from the money spent.