fisher, I'd agree that a good cleaning and setup might cure your problems. How this gets accomplished depends a great deal on your expertise and comfort with carburetor surgery. If either or both are low, some help would be in order! Are there any other Model A enthusiasts near you in Scotland, among whom might be a carburetor expert? Second best would be to get your hands on one of the published booklets on rebuilding them - these are available for both Zenith and Tillotson. Good luck!