Rent agreed, what action needed to follow up?

Tenancy Types and Management

I have just agreed a rent increase with my current tenant of over 10 years. He is on a Statutory Periodic Tenancy because the old AST expired some years ago. The new rent is still about 10% under market rates for the area, and I am happy with that due to his good behaviour - see below.
What action should I take now to cover my backside if things go sour in years to come? The subjects I am thinking of are:-
1. He's quite messy and the house is very cluttered. Renovation work may be held-up if the trades can't access their areas effectively.
2. I want to keep open the option of selling the house within 5 years.
3. During the rent negotiation he made claims as to a number of maintenance problems that he's done for me over the years without notifying me (until now), some of which are difficult to believe. If I don't refute them now will this be seen as acceptance by default?

Still, he's been a nice tenant, he gets on with his neighbours and with me too, so he's an asset in many ways. I don't want to annoy him, but I do want him to clean up his act ahead of the refurbishments, avoid any conflict with the trades, and ensure that I am not hanging a millstone around my own neck for the future.

It has been suggested that I ask him to sign a new AST contract for 12 months, but are there any variations on this that will give him more security of tenure whilst allowing me to increase the rent by inflation every year?

P