Dealing with rent arrears

Rent Arrears

I had a tenant for 9 years. I sent a S21 recently. When looking through the payment history I noticed there were 2 amounts unpaid from long ago. It was my fault for not noticing and leaving it for so long. it was mostly because of the way he was paying, in bits and bobs , different amounts, not paying on time etc etc and also because I had been extremely busy. One is dated as far back as 2004 and one is in 2007. Over these 9 years I have two bank statements missing and barclays bank which is my bank said they do not keep statements for so long. I would have thought they had to because HMRC can go back upto 10 years if they want to.Any way, when I gave the tenants notice to leave last year they were begging me to reconsider etc because they have a child, I sent an e mail saying if they pay these arrears, and bring everything upto date and pay on the due date we will continue with the contract. He had written that his bank only gave authorisation dates going so far back and said he had paid 22nd of Dec 2006 which should have beem in my account for Dec 06 and it isnt. however; I dont have the Jan 07 just incase it went in then but I know from the brought forward balamce that he has not paid. Also he has said I have accused him of being a thief and it gave him depression and his christmas was spoilt etc. he seems to make these false allegations even when I send a nice frienly e mail. I am reluctant to send another e mail about these amounts unpaid and would rather let some one like Legal4Landlords deal with it. Can I ask him to prove that he has paid because I dont have a couple of statements?. Also he has sent me a list of 13 months from Dec2006 to Dec2007 which is 13 months and he has stated he has made 12 payments which itself proves he is one month short. If I send an e mail stating this he will inundate me with allegations which he is very good at. I feel he is trying to build up a case of harassment when its he who is harassing me and I have heard stories where councils encourage this and actually help them to take court action against the Land Lord which is something I want to avoid at all cost as I am not well enough for these kind of stresses. What is the best course of action?

perplexed