Its seems from a lot of episodes, especially those with Foggy and Seymour he was a professional Crash Test Dummy and Stuntman. A Wellie tester for Dunlop maybe?
Compo seems to suggest a few times that he did work a bit here and there. Based on most of his ladies being dumper drivers, wall builders, etc., it's probably a fair guess that he was involved in some sort of manual labor type jobs. That was before he convinced doctors that he had a bad back and got put on the disabled list.