Is that rent "150 pounds less than three years ago", or "150 pounds, less than three years ago" ?
If you are only getting 150 a month you are being screwed; rents are about 400 pounds for a two-up two-down in most areas (unfurnished).
A lot of people have now dumped the whole asylum seeker/DSS tenant market in favour of ordinary tenants who are working and will pay around 400 pounds, less hasssle too. The lower end of the market, where you are working, is full of problems and grief for landlords.
You didn't say which area in Manchester you are in. Might be better options than the one you are using, although 12% plus v.a.t. is ok if they are doing the business for you.