Barmaid is correct. To evict you, the landlord has to issue you with a written notice under either section 8 or section 21 of the 1988 Housing Act. In this case, it would be section 21. This notice gives you TWO MONTHS notice that the landlord intends to seek possession - it DOES NOT mean that you have to leave on the expiry date, the landlord has to go to court to 'seek possession' and that process will take a couple of months.
You can not be served with a valid section 21 notice if your deposit is not in one of the 3 government approved schemes.