You're in Glasgow? You should be able to find a kosher butcher, kosher supermarket, or kosher deli. They will 100% have what you are looking for.
If you go to a butcher or supermarket you may be able to get fresh boilers. Sometimes whole birds, sometimes half birds, but always with the skin and bones. Almost guaranteed also, you can find a 5kg bag of frozen boiling quarters. It's usually 3 breast/wing quarters and three leg/thigh quarters. This chicken can be cooked from frozen.