I'm surprised, a quick search on the going rate in Milton Keynes and the results aren't much different than London suburbs, averaging £400pcm. When I was studying I was paying £450pcm outside london.
My phone contract was a sim only deal for £15, alcohol was a once month thing.No car at that time but nowadays I need it for work, but then, public transport in the UK is not cheap anymore.
About spending £120 in food, you must have no meat on your bones then, as a bloke who stands at 6'' ft and 100kg(muscle), that figure is not enough.
Not sure if you are trolling us, I think you can achieve those savings if you're living with you parents and they are kind enough to let you off the hook, otherwise I'm not so sure.