I personally recommend the Oxford MCC course. A modular student, me, who had no other experience of OAT, found this course extremely good. Using full motion 737 classic generic sims is great fun and the course is designed to be relevant to your future daily life in the RHS, which it is.. I speak now from personal experience.
Doing it as cheaply as possible is one way of looking at it, but if you spend a marginally larger amount (in the grand scheme of things) you will get a lot more out of it and will take the benefit of that on to your first job.
Rb311