Landlord & Tenant Dispute

[JimP]

I run a small property company, one of our properties comprises a ground floor office suite with a residential flat above. The flat is let on an AST to a young lady with a little boy of three, now the boy is on school holidays he spends quite a lot of time in the flat running about. The office tenant is now claiming noise nuisance and breach of his quiet enjoyment and is saying he will adjust his rent accordingly. I have spoken to tenant in the flat on several occasions when she has promised to try and keep him quiet however it has had little effect. I am really at a loss to know what to do next. Please can anyone help?