Visiting parents

Other

I have 2 chinese tenants of longstanding in a 3 bedroomed flat. They have just e mailed me to request permission for their parents to stay in the flat for a 3 month period commencing in June 2013 during a ho9liday visit. In addition they are requesting a letter from me "to whom it may concern"stating that my accommodation is suitable for the additional "temporary" tenants. They have provided the names, dates of birth and passport numbers of their parents.

The tenants have always paid their rent on time and kept the property in reasonable order. I am unsure whether or not I need to have their names added to the tenanct agreement. Or obtain some form of supplementary agreement to protect my position. In princile I have no objection to their request and am pleased that they have notified me. I am wondering why they need my written assurance that the property is suitable. I am thinking that this has to do with immigration isssues. If this is the case then clearly the "3 month holiday request" may in fact turn into a permanent situation.

Sorry to pose such a complcated question and hope someone can advise.
Perhaps I need to consult a legal expert?

Andrew Cookson