Extending a tenancy

Tenancy Types and Management

My first tenants have been in the property for nearly 6 months and have indicated that they'd like to sign another fixed contract, for longer than the initial one. They are good tenants and I'm happy to do so. If I don't offer them a longer tenancy they may feel I'm getting ready to push them out, which I don't want to do. My questions are as follows:

1) People have suggested on this forum offering a year with a six month break clause. But surely a year contract or longer with a six month break clause is no different from a 6 month contract is it?
2) Or is the only difference that if the break clause is not used, it does not become periodic until after the fixed period ends (one year or longer if stated)?
3) Are there any other restrictions on offering a longer fix (eg do mortgage lenders prefer you not to? I'm just about to move my mortgage).