Sime Gas Valve
part no 6243820
it will fit to following:-
Sime Ecomfort 25 HE
Sime Ecomfort 25 HE System
Sime Ecomfort 30 HE
Sime Ecomfort 35 HE
Sime Ecomfort Plus 25 HE-EV
Sime Ecomfort Plus 30 HE-EV
Sime Ecomfort 30 HE
Sime Format C 100C
Sime Format C 110C
Sime Format C 80C