I have purchased a property with an existing tenant

I am an experienced landlord but have never dealt with the following situation. I have just acquired a property with a tenant and a 6 month AST is already in place. This existing AST is due to run out on 30th September 2009. Is there any notice I should give the tenant that I am the new owner/landlord in anticipation of having the tenant sign a new AST with me on 1st October 2009?

Any other general advice regarding this matter will be gratefully received.