Hi Julian,
This post (2 strings below your post) has a link to a map with couple of places near Doncaster:-
I’ve recently had the rear wheel arches on my Mk2.5 repaired, using repair panels, welded/painted at a garage local to me in East Yorkshire.
I hope you find a good local garage.
The Yorkshire Ridings use Facebook to communicate, rather than this MX5OC site. It might be worth joining their Facebook group and asking for recommendations on there.
Good luck, George