Hi Mark
Apologies if I am pitching low but have you adjusted the idle speed on the carb? I have a TS250/1 and on that bike the left hand screw which has the screw head angled downward is the idle adjust. The further you screw it in the higher it pushes the throttle body and the faster it tries to tick over. The idle mixture screw to the right will also be important. Set it as per manua,l for mine its 2.5 turns out. Set it at the manual recommended position with a healthy idle speed and see if that does the trick.
Failing that check the voltage coming off the regulator. I had trouble for ages with a lumpy idle and constant stalling at standstill, much worse with lights on. When I changed to a an electric regulator the bike was transformed.
Rhodri