Want to sell but not sure if I can evict?

I have a rental property that my tenants have been in for five years. Last May they asked for a ten year contract which I was happy to agree to as they are good tenants and had no intention of selling.

December just gone they decided the house was too small and they wanted to move out, not wanting to cause a fuss I agreed they could get out of the contract and go their way. Then a few days later they changed their mind and decided to stay. Reality was they missed out on the house they wanted. This got me in the mind set I was going to lose good tenants and couldn't be bothered with the whole rigmarole again of finding tenants and decided it's time to call it a day.

So I've come to the conclusion I want to sell and get my money out the house.

The tenants have nine years left to run on their ASSURED SHORTHOLD TENANCY AGREEMENT, you can read a copy of the agreement here www.zerowords.com with names and addresses removed.

My question is where do I stand? Can I issue a section 21 with 2 months’ notice or am I stuffed and until they decide they want to go or the contract runs out I'm stuck with them?

Any help would be appreciated.

Thanks

Nick