Student funds can be limited, but paintballing is no more expensive than loads of other things students get up to. Smoking for example. 10 a day at £5/pack adds up to £912/year. If you get you an ion (£150), bottle (£60), and hopper (£40), go to a dozen training sessions/walk-ons (12 x £35 = £420) and a 4 KotH tourneys. (4 x £60 = £240) that would cost £910, meaning you've got £2 left over for a pint and as an added bonus you don't have cancer.
Of course you might want to spend more than than on paintball, but I was just illustrating that it is possible to play.
If you are going to Portsmouth then it should be even easier. As with most university paintball clubs, Portsmouth get financial support from their Students Union/university. Also the Uni league we are running next year is going to be very light on the wallet. And another advantage that is emerging for uni teams is the availability of gyms for doing reballing in. This will allow you to do weekly training for a pittance.
And avoid the pitfall of blowing your student loan on a flash gun and then not having enough money left over to train and play.
If you want to get anything more than an ion, check in advance that you will be able to afford to play with it. If you will, no probs, but if not then consider whether it is really worth having gold plates... but no food.