Although not a million miles from my depot I’ve had to pull the curtains a few times in Ayr and the racecourse was ideal but more recently I’ve used,
1: As GOG47 Says Heathfield retail park but don’t stop in the service yard area, stop on the road between the retail park and Asda
2: Promenade of Saltpans Rd but to be honest unless your a real heavy sleeper this aint the best, the sea battering about allnight can get a bit loud. Probably a last resort type of place
3: Nice big deep layby on the A70 a mile or so of the A77, not much about but ok if you self catering . There is a snack bar during the weekdays but not sure if it’ll be ther early enough for your breakie.