I was renting a house out for a weekend however was let down by other people who were going to stay shoukld I lose all of my deposite if I let the vendor know 3 weeks in advance

If it was my rental you would, what was the rules of the rental as to deposit and to the time you had to cancell ( if you were even allowed to)

You are bound by the contract you agreed to with the landlord

This is where it gets interesting, he sent me the rules after I had paid and so I didn't actually agreed to anything. He has said now that if he gets another booking that I will get it back however if he does not get another booking will not allow me maybe come for just one night so as to get something for my money already paid. The house was quite expensive so have paid a lot which was only half.