Hi you could try this guy Stuart Gorman, I had a seat recovered he did a good job and fair pricing
Gorman Services
75 Main St
Baillieston
Glasgow
G69 6A
0141 771 2540
enquiries@gormanservices.co.uk
Cost me £20 about 6 yrs ago, to have a zip replaced at a leather repairers in (Lockwood) Huddersfield.
I think £20 were his 'across-the-board' charges lol. When I had a piece put into the lower leg, to make the hem wider so I could get them over my boots, it was £20
Soz, I can't help with the Glasgow repairers.
If you haven't found one, there is a great guy new Kilmarnock at Grassyards - he is a saddler but took in my leathers really well and his price was very reasonable - I can get you his phone number if you want it?