Landlords rights! Please help.....

Other

I have been renting out my flat since last year as my circumstances changed ie job move! I'm sure there are lots of other people who find themselves in the same position as me, the relutant landlord! With the current housing market this is sure to increase. I asked the tenant to sigh a 6 months agreement giving me two months notice of their intention to leave in writing and vice versa... On signing a 2nd 6 months AST I'm now informed that the tenant need only give me one months notice? Can someone please clarify? The tenant has since left & left the place in a complete mess, with many appliances broken and damage to almost every room in the flat! I was so upset and concerned that I managed to get hold of her current landlord to inform them of my situation and to warn them to make sure their property does not go the same way... I have since received a letter from a solicitor acting on behalf of the tenant saying I'm saying untruths about her & if this continues I'll get into trouble!