My Commercial Landlord Has Changed The Room Where Our Group Meets To A Smaller Unsuitable One. Can He Do This Even Tho' We Had Booked The Bigger Room Well In Advance?

We lease a number of rooms twice a week at a local hotel. Recently the business manager approached me and told me that these rooms would no longer be available on the dates we'd asked. They do not appear to have anyone else coming into the rooms as at the first meeting they agreed to let us use our usual room. I have been asking for a written contract from them since Christmas 2007 but had managed to get from them a verbal agreement to give us two months notice if the rooms were unavailable.