For income tax purposes, there is an exemption where you rent a room in your house. If annual rents are at or below £4,250 per tax year and you claim the 'rent a room' exemption then you will not pay tax on those rents.
If you look at HMRC's Inspectors Tax Credit Manuel (link below)
I rent a spare room on a Monday-Friday basis to a professional female. It's nice company, the dosh is a HUGE help and at weekends the house is all mine and DS's again. Took a while of advertising to get a Mon-Fri person but I was determined I wanted privacy at the weekends. And as Winnie300* says, as the monthly rent is below £350 you're fine for tax purposes. Go for it!