Possession for arrears etc

Possession - Section 8 and Section 21

I have two tenants in arrears and I plan to evict one as there is little hope of him recovering the situation on top of which the property has become a mess with rubbish all in the garden, the house is filthy with minor damage too.
The arrears of the latter are in the order of 5 months so I am assuming a 1 month notice under section 8 is my best route and not to back it up with clause 13 for the damage and general condition of the property as that will extend my notice automatically to two months?

The other tenant is almost 6 months behind so I assume the same 1 month section 8 period of notice if I can not get a reasonable debt recovery plan agreed, which is my first option with these tenants.

I had thought I may sell the properties as I am currently developing new houses elsewhere and the money would be very useful.
I could not see the clause for wishing to sell your house, has this been removed altogether?