I would suggest you opt to take the Commercial Seamanship Exam - it is only a few questions more and the syllabus is the same.
We can provide the details of the books and syllabus, plus various learning/briefing docs. Also most of the questions and answers (but don't tell anyone!), as e-mail package for $75.00. As there are few applicants for this exam in the UK, the questions are rarely changed. You should of course make sure you read and understand all the appropriate Rules in the syllabus, for instance: the buoyage system is different, rather than just learn the questions!!
However, if you want a structured Course, On-Track is fine.
Normally you sit the Exam at CAA London Gatwick, on a date that is mutually agreed with them. You sit in the back of another exam and then sneak out when you have finished the short Paper. I am unsure whether On-Track have negotiated sitting exams at their location in the Midlands.
Hope this is helpful.