Hey, I was recently in the same situation as you. I went to specsavers, the eye test cost me £5 (it was a promotional offer, I think it is still on). Then chose new glasses, you get a range (£25 cheapest I saw to designer ones £125). As a student you get discounts too but it wont be used in conjunction with another offer. I got a £69 one, which meant I could get the lenses thinned for free but could not use my student discount. Then they give you a date for when to collect it. Regarding contact lenses, you book an appointment, get eye tested again, I did not pay for it and then another appointment to teach you how to put them on/take care of them etc. There is a 30 day free trial on right now. They range from £18 to £25 depending on the quality and how you want to use them i.e. daily etc.
Hope that helps, also you can just pop into a local store for more help and leaflets