Hi Blue sky - I've been investing in Manchester for the last 10 years. We did have several city centre flats a few years ago, but I would not recommend this strategy. The main reason being that the rental market is saturated with flats and competition for tenants is high, landlords offer lots of reduced rents, plasma TVs etc to get tenants in. Once they're in they usually stay for 6 months and then move onto the next place offering freebies. Also young professional tenenats like to be in the newest trendiest complex, yours maybe "it" now, in 6 months time another will be "it". We ended up with flats being rented for only 9 months of the year, and couldnt make money this way.
If youre buying for capital gain purposes, it may be another story - I dont know.
We've brought houses now valued around £120k in areas very close to the centre, Ancoats, Levenshulme. Not particularly nice areas, but good for long term rental to working families and continued capital growth.
If you really want to spend £400k on one property I'd look at Sale, Altrincham.
Good luck.