Rent Increase

Tenancy Types and Management

I want to increase my tenant's rent quite substantially (by £95 per month). She has been there for 2 years when the current tenancy agreement ends in November and she has never experienced a rent increase. So this month I plan to give her 2 months notice of the increase in November. Can I increase the rent by this much or is there a law that restricts the amount of increase. Your website advises the rent increase should be in line with similar properties in the area, the problem is, there aren't any reasonably close-by.