Mr Sam,
We've been investing in the Manchester area for the past 15 years or so. I agree recently it's been pretty hard to make a measley 7%, The worst rental markets are trendy flats and run-down terraced houses for students - over satuated. Rentals are quite good for standard 2 bed terraced houses, young sharers or families, but house prices have gone up from reasonable £70ks to over £100k.
If it was rental income alone I wouldnt bother. But there are still some areas where regeneration is occuring (moston), new tram lines(Rochdale) etc and 7% is fairly likely to become 10+% in say 2 years and you stand a reasonable chance of capital growth too (even in todays market). Morecambe larger family properties are reasonably priced, but I havent looked at rentals yet.
Your example above, I'd say the house prices have risen recently, but rents havent yet (expect a 12 month delay). I'd either expect a grotty house for £50k/£240pcm rent or a (less) grotty house for £70k/£400pcm rent.
Have a look at Edward Mellar Auctions (and others), they sell a variety of terraces in different areas. I think last months auciton sold well, but the previous one didnt. Not sure what auction finance is available though.
In summary, I think my message is, there are still some good areas to invest in the NW, but you have to be very choosy, maybe even down to the exact street and you may have to take a loss for a year.