Tenant Threat of Rent Tribunal

Other

Dear Sirs,

I have rented a property to the same set of tenants for some five (5) years. An initial fixed term agreement became “periodic” for a while before a further fixed term agreement (still current) was signed. The asking rent has been significantly higher than "street average" throughout the five years although - unfortunately - there have been several major repairs necessary (boiler replacement/ part rewire) which - despite reasonably prompt rectification - caused the tenants a vexatious level of disruption.

It is now possible I will have to evict these tenants for rent arrears. They have threatened to go to a rent tribunal in retaliation.

My queries are:
1) What is my potential liability wrt the tribunal threat? (ie for the entire five year period, latest fixed agreement term etc)
2) Would the major repairs be likely to factor against me? (despite my prompt action)
3) Would my liability wrt the tribunal be moderated by limiting my proposed eviction to a S21 notice (rather than a joint S8/S21?

Thank you for your assistance.