Is it your own place or rented from a landlord?
Depending on how old the carpet is, a reasonable landlord might be able to replace it when you leave as part of their normal 'wear and tear', as they're supposed to redecorate and replace furnishings every so often, as they claim tax breaks. Although they will probably try to keep your deposit.
If it's your place and you need a new carpet, there was a carpet place in Whalley Range, opposite-ish a Tesco metro or express, I think they were called D Hall. They relocated from the main road to somewhere behind the Tesco I think. Haven't been to their new building, but I bought from them before. You can get some really reasonably priced end of roll bargains, and their fitting charges are reasonable too.
The carpet that replaced it isn't as nice. 
