None in the centre.
There is a gunsmiths called T. Stensby and Co. but wouldn't recommend them. They do stock some air rifles but they're mainly into powder burners a IIRC - they're a shower of miserable #######s!
There's Manchester Airguns in Failsworth which is about 5 miles north of the city centre.
The Mayor: Intent? How did you establish that?
Harry Callahan: When a man is chasing a woman through an alley with a butcher’s knife and a hard-on, I figure he isn’t out collecting for the Red Cross.