RLA AST queries

First - is there a reason why it doesn't make any provision for rent increases? At the following URL
<http://www.rla.org.uk/landlord/documents/useful/doc_S13_RentIncNot.shtml> it states:

"If the Tenancy Agreement makes no provisions for the landlord to make a rent increases, then you have two options to increase the rent:
- Renew the contract at the end of the fixed term but at an increased rent. OR
- At the end of the fixed term, serve a Section 13(2) Notice of the Housing Act 1988, proposing an increase in rent."

Now, I usually want to keep my tenants on a periodic tenancy after the end of the 6-month fixed period, and I'll most likely want to review the rent at 12 months, which involves the aggravation of an S13 notice. So, what wording should I include in the AST to circumvent this and is there some reason why the RLA version doesn;t include it?

Secondly - the AST mentions a penalty interest at the rate of 3% over the Royal Bank of Scotland base rate (which is currently about 5.5% I think?). However, as I'm currently in the middle of a small claim, I know that 8% is the rate which I had to claim at. Where does that figure come from, and isn't that what the agreement should use? If not; why does it quote the RBS base rate (which I actually can't find anywhere!) rather than the more obvious and readily available Bank of England rate?

Thanks.

5.75%