Taxation in the Uk

[Ray32]

Ive already been letting out a room in my flat for some time now and my understanding of Uk taxation is that I have an allowance of faround £7,500 per annum.  I was wondering if I rented out my other room wether HMRC would view this as a business and disallow the allowance on the first room??  and tax both room incomes  at 20%?

[Gerry-And-Rashid0]

My understanding is that it matters not to HMRC whether you are getting income from a sofa, a single bed or renting out two rooms. There is an annual limit after which you must declare it on a self assessment return.