Your best bet for a large kitchen with relatively easy access in the UK is going to be a pub that does food, where the guy running the place is the owner and doesn't need to get permission from the brewery and, because you're a student, it makes sense to go for a pub that relies a lot on student trade.
If you're at a college rather than a university you could check out the facilities used by the catering students.
A couple of points though.
Student films are notorious for being disorganised and also for being stupid when it comes to thinking through the implications of using a location. It's fairly easy to get free locations, but hanging onto them gets hard once the person who has given permission starts to understand what's involved.
So, here are a list if things to think about:
1) How long do you need the location?
Seems an obvious and simple question, but lack of scheduling experience and student unreliability can turn your projected two hour shoot, into an all nighter.
So, before you even seek permission scale your cast and crew down to the people who you can absolutely guarantee will turn up to the location on time and who once there will get the job done quickly. Nothing will screw your film faster than saying your people will be there at 11pm for a two hour shoot, only to have your people wander in at 11.30 and then spend an hour messing about with lights and another hour of the director and the DOP arguing about shots.
Make sure that before you even ask for a location, you have a locked down plan of exactly what you want to achieve and how you're going to achieve it. Storyboard your shoot and calculate your location time from your storyboards. Give yourself a margin.
2) Are you going to do anything that represents a Health and Safety risk?
If you're planning to do a Nikita style shoot up in this guy's kitchen, involving squibs, broken crockery, or anything that might cause an accident you're placing a liability risk at the owners door. Someone gets hurt in his kitchen, then he's going to be in all kinds of trouble.
Even if you're doing something you may consider safe ... ie. cooking, this involves his ovens being turned on and the possibility that an untrained actor will burn herself, cut off her own fingers with a carving knife or cause a spillage that creates an accident.
So, this means creating risk assessment documents for the shoot showing that you've identified any risks and have taken appropriate measures to ensure a safe shoot. Which includes safe rigging and securing of your lights.
3) Are you going to make a mess?
It's a fair question and the more mess there is going to be the harder it will be to secure your location.
I know you may find it hard to believe, but I've known any number of students film makers who have trashed a location and then left it for the person who kindly gave them the space to clean up.
You need to be able to reassure the guy that they'll be minimal mess and that your crew will leave it as it was found, within the time frame you've allowed for your shoot.
4) How little kit can you get away with?
Student film makers often make the mistake of thinking lots of kit makes for a better shoot. So they'll automatically bag in every redhead they can get their hands on, simply because having real film lights makes them feel like real film makers.
On a free location you want to work with the absolute minimum of kit. In particular you want to scale your lighting down to the lightest, safest option that will do the job.
Red heads get incredibly hot, take ages to set properly and represent a genuine hazard (as when the bulbs go, they invariably set fire to something!)... if you can manage without them, try to.
Basically, what I'm saying is this: before you ask for permission to shoot somewhere you have to have a plan in place so you can answer any of the owner's quite legitimate questions.
If you can do that and then follow through on your promises, then you'll not have any problems securing your location.
The main thing to remember is this -- even if you've been promised a location for three hours, that location can be taken away from you at any point if the owner feels they are being taken advantage of.
Getting a location is easy, but so is losing it.
Once you've got all these points hammered down, all you have to do is make a list of possible locations, walk in, introduce yourself and ask if they can help.
Truth is, most people are only too glad to help film makers with locations (especially if they've never done it before! LOL)