I very much doubt that you'll find left luggage lockers anywhere now - for security reasons the only left luggage facilities at any airports or railway stations etc are staffed ones with X-ray machines for screening the bags first before they are accepted. Imagine the consequences if terrorists could just leave a bomb in a bag in a left luggage locker and be well away before it was detonated.

SM

Network Rail Manchester Piccadilly, has a left luggage, as has the airport, but as has already been said they'll be manned and I would imagine a tad expensive..

http://www.networkrail.co.uk/aspx/921.aspx

There is a properly manned private left luggage office (not 24 hours) about half way down platform 10 at Piccadilly. If you are approaching from the entrance it's obscured by the Northern Rail customer service office. They charge per item, if you have only 1 bag it's not too expensive but if you have 2 bags that would fit in one locker it gets pricey.

Anyone planning to use it on a big event day (like when Rangers played Moscow!!!) be warned it only has very limited capacity and your chances of getting in are slim!