Seen a fantastic house that we really want (to rent) but on checking our existing tenancy agreement we realised it is for a "definite period" i.e fixed and it runs until the end of August - the other house is available end of June so I can't see the landlord waiting until September for us to move in. Bugger. High demand for rental properties round here and we have very specific requirements. I wish we had checked the tenancy agreement more carefully now - we had to sign up in a hurry (long story) and we just assumed it was a normal shorthold tenancy which we could give notice on after the first 6 months. Bugger!!!
You may find if you can get another tenant in the landlord will be prepared to break the tenancy agreement, it's worth asking at any rate. Fixed tenancies can be better for both landlord and tenant in terms of security but work against you in cases like these. For the landlord, the main thing will be not to end up with a period of the house being empty.
Thanks for the ideas - yes we are going to try and make it work even if we have to run both houses concurrently for a month! Just surprised me really, I always thought that once the initial 6 months were up you could always give notice on a tenancy.
I know this doesn't help now but when you get to the end of your tenancy agreement, in August, don't sign a new agreement. If you don't sign (and your lendlord can't force you to) you will go onto a Statutory Periodic Tenancy that you can give notice on at any time.