we do not have a contract
Unfortunately, the situation you are in is not favourable. Whilst the landlord cannot double the rent and you would be entitled to take him to court to have the rent set the market rent, because you have no tenancy agreement you occupy on a tenancy at will/licence and if you don’t agree to the rent can simply give you notice to quit.
Even if you did have a tenancy agreement it may be that the original rent was extremely low and all he is now asking for is the market rent although because you have no agreement and therefore no security of tenure, it is actually of no consequence.
I’m sorry that this is bad news for you.
Can I clarify anything for you?
where would I get the data what is market rent