Unless there is a specific clause in the tenancy agreement (not common but it does happen), you must issue a Section 21 notice for at least 2 months. Also make sure it is issued on the rent due date which in your case would be 29th February giving an expiry date of 30th April, issuing on any other date will render the notice invalid. There are several sites on the net where you can download copies, just google Section 21 notice.
The Rent Deposit Boards were set up to alleviate the problem highlighted by Nibble with too many landlords retaining bonds on the flimsiest of reasons. They should act as arbiters in any dispute but their effectiveness varies from area to area.
This is what happened to me, issued the section 21 but as soon as I did, they stopped paying rent which left me 3-4 months having the twats from hell in the property but no rental!
Because of this, I now have council tenants there. The reason for this is, the council pay me the rent bang on time every month direct into my account.
Secondly, they guarantee the deposit. They have their own people come round and do a full and concise inventory of absolutely everything.
That combined with my own insurance combined with malicious damage, gives me a bit more peace of mind