I'm not sure where you're going in Manchester not to find it busy. Then again, I've not been for a good few years. I sacked it off due to the rip-off prices and it being too hammered to enjoy it. I get my Christmas market experience in Germany these days and it knocks the Manchester markets into a cocked hat - far cheaper prices for food and drink, and not too overcrowded. In recent years with the other half I've done:
Cologne
Munich
Aachen
Dusseldorf
Nuremberg
Rothenburg ob der Tauber
Plus Moenchengladbach when City played there in 2016
In a few weeks we're off to Leipzig and Berlin - 3 nights in each