Hello I am a solicitor with 20 years experience. I will try to help you with this.
When is he demanding the rent increase from?
If there is isn’t a provision in a fixed-term agreement for the landlord to increase therent, the rent will remain the same unless you agree to a rent increase.After the end of the fixed period, or wherethere has never been a fixed period, if there isno provision in the agreement for a rent increase unless you agree to an increase, thelandlord must follow the procedure set out in section 13 of the Housing Act 1988.Under the procedure, the landlord must give you at least one month’s notice in the correctform. The notice must advise you of your right to refer the proposed increase to theFirst-tier Tribunal (Property Chamber) – formerly it was to the Rent AssessmentCommittee (RAC) – which can assess whether the new rent will be above a reasonablemarket rent of similar properties in your area.If the new proposed rent is too high, it can be lowered, but please note that if it is lowerthan the market rent it could be increased.Under this procedure, the rent can only be increased once a year. It can be used when the fixed term ends.
Basically he has no right to increase your rent during the term of the agreement.
If you refuse then he has the right to take back the property at the end of the tenancy ( he has this right whether you agree or not). There is nothing he can do during the tenancy.