Unfortunately, even in one-make series, some are more equal than others! Theoretically, you'd think everyone must have the same machinery if they're all built to to the same spec, but in the real world, that's not always the case.
Those with the bigger budgets will always find a way to gain an edge - even if it's only as simple as having the time/money to go testing extensively, paying for a professional set-up on the car and having new tyres/brakes for every meeting.
You, on a student's budget, are unlikely to be able to have those things, probably won't be able to afford to go testing, or have a professional team set up your car for you, and will most likely have to use your tyres until they're down to the canvass!
I'm not trying to put you off the one-make route - but just have your eyes open if you go that route, and accept that you're unlikely to steam in and be on the pace against the experienced guys with big budgets.
As has already been said, if you're not stuck on the one-make idea, there's a whole world of club series out there, and many of them offer much better value than some of the one-make events. Just take a look on the websites of clubs such as CSCC, 750 MC, BARC, BRSCC, CTCRC, etc. I'm sure you'll find something you fancy amongst them!