Heald Green, South Manchester. Near the airport.
I think they have directions on their website: soundsgreatmusic.com
Heald Green station is 15 mins walk but driving from Dewsbury can be done in an hour. I live on the doorstep of Sounds Great and I can make Huddersfield in 45 mins.
If you do go, make sure you ring them first, as they change stock all the time. The staff will let you try anything even if you are not going to buy, hence, I'm in there a lot :D