Please inform how much money should I have to cover 3 years of living in UK?

You will need at least £500 per month to cover rent, bills and food. There wont be any left over to go out very much. If you plan on doing this you will need more.

I would say 500 is a minumum - allow up to 700 if you are going to live in an area where you might need a car/ travel extensively.. It also hugely depends on where you are planning to live - countryside, city or especially London as rent specifically varies widely throughout the UK

This website may help:

www.infozee.com

It also depends on where you'll reside; London in particular will, as mentioned below, be considerably more expensive. Personally my rent alone will be £475pm for a swish studio, leaving £525pm. I'd estimate £100-200 of that going to food and other expenses. So overall I estimate circa £700 in my case.