Can anyone advise me, a landlord trying to do the right thing?

[springlamb]

After a silly landlord/tenant dispute last autumn (our first in 8 years) my long-standing tenants told me they wanted to move out when the tenancy ended (March 2010). Although dispute was resolved and I reassured them I was happy for them to stay, they were adamant.
So after Xmas I told them that I felt I had to issue them with a notice to quit. I intended to give this on 21 January, making 20 March their last day. The tenant asked if they could stay until Easter and move over the holiday weekend. I agreed and in fact said that we could extend for a month and that they would need to be out by 20 April. So I didn't issue the notice.
But now I feel (even though I'd still welcome them changing their minds) that to protect myself I need to issue a notice by 21 February requiring them to vacate by 20 April. Would that be the wise thing?
I have no reason to doubt their integrity, they have been fab tenants and I'd recommend them anywhere, but personalities aside, it's a legal matter isn't it?
They've been there so long, and such exemplary tenants, I haven't had any dealings with solicitors for yonks and don't really have any contacts to check with.

Don't really understand - has something happened in the meantime that means that you now have a reason for wanting them to be out by April 20> In which case yes, I think you should issue a notice to quit. I always do this with our tenants as we have always had new tenants signed up (quite a long time in advance) of their agreed leaving date (student rental).

PS - I always cover the notice to quit with a note explaining that it is just a necessary formality and provide them with the instructions for handover and deposit return process.

Thanks. I just have a slight worry that if I don't issue a notice and they haven't sorted themselves out by Easter, they will want to stay another month etc. They haven't put anything in writing themselves. I don't want to degenerate into anything informal. If they are going, then I'd prefer a swift cut-off, and get someone new in on a 12 month tenancy. And my understanding is that if they did stay on and it all went pear-shaped I would have to then wait 8 weeks to get them out.
I think I may talk to a few property management cos for the next tenancy, I am obviously out of practice!

Well yes - if you don't do anything they will probably just assume that the tenancy will move to a month to month as is usually the way at the end of a short term assured. And yes, when you want tenants to leave you always have to give them at least 2 months notice.