Add ons to AST

Tenancy Types and Management

Please can you advise on the following :

I am a first time landlord and set up the AST for 6 months ( due to expire in October 2010 ) but added the following 2 add ons to the AST and not on a seperate addendum sheet ( I just squeezed them in ). The tenants were aware and agreed to the the add ons. After reading more about the addendum procedures on the website, I am now concerened that I haven added to the AST illegally,

please advise HAVE I DONE SOMETHING ILLEGAL ??

The add ons ( exactly as written )
1. no smoking anywhere inside the property including the utility room
2. Not allow dogs into the living areas of the house. They are allowed use of the utilty room.

Note :( i was aware at the outset that they has dogs and they happily agreed to the above)

Many thanks for any feedback/advise that you can give me,
Kindest regards
Sid and Gill