No current agreement

Rent Arrears

I have had the same tenant in my property for the last 6 years and we have a friendly relationship. However she is now nearly 3 months in arrears. I go round regularly and one time she had her brother pay one months rent but then paid nothing herself and so the account was still in arrears. I am not sure if we have an up to date contract - the last one signed was for 2 years but I cannot locate it and am unsure if the 2 years are up now. In the 6 years there have been times when there was no contract - I work and this was the property that my Dad owned. The tenant had always been good, even with work needed - sometimes doing it herself and being reimbursed. The fridge freeser broke down and she wanted a bigger one than the one I had ordered and so said she would pay the extra on a bigger one and she still has not paid that £110 either.
I am worried that she intends to leave with a big debt - I was there yesterday and the bins were empty but there was still things in the room that I could see from outside. I have very little money - have an arrangement in place with the mortgagor now and have money to pay over to ex-husband following a divorce settlement. Could you please advise my next moves?