Northern Dance Services bundle: 30 x 7" singles, strict tempo ballroom dancing

Looking to recreate Strictly in the comfort of your own home? These are for you. A bundle of 30 x 7" singles from Northern Dance Services of Shipley, Yorkshire, intended as strict tempo accompaniment to ballroom dancing from the late 60s / early 1970s. There's a whole range of styles - tango, bolero, cha cha, quickstep, waltz, you name it. Some are 45rpm, some 33. The main appeal of these, for me, is the incredible artwork, but some of the music is fun, too. Sleeve condition is generally not great - there's ring wear and discolouration, with occasional sticker residue. Discs are dusty, but I don't see any permanent marks, so I think would play well after a clean.