The other tenants are friends of mine and are happy for my partner to move in. We split all the bills other than council tax between us. We currently pay £35 each in our rent towards the council tax. I didn't think that there was anything law wise I could use to back up an argument to pay less but thought I'd check. As you say it's up to the landlord to decide what they want to charge and us to accept it or move on.

My partner is going to move into my rented room with me which is in a shared flat. I am paying £370 for the room currently and our contract is up for renewal at the end of the month. The landlord is happy with her moving into my room but is going to charge £170 (half my rent value). This means we are now paying ~£540 for the room which is £140 more than my housemate pays for a room twice as large as mine. The landlords justification is that this is an industry standard (i.e. to charge half rent to the second person) is this the case? Apparently its to cover additional wear and tear. It seems more like greed to me as the deposit is to cover any damages and wear and tear should be expected and not covered by the tenant, especially not to the tune of £170/month.