The Britony SE is an automatic ignition applance and doesn’t have a pilot light, a spark generator does the honours of lighting the gas.. if the gas supply has been interupted the boiler will ‘lock-out’ and the reset button on the SE’s sometimes doesn’t fully press the microswitch that is on the main pcb behind the fascia.. try switching the boiler off at the fused spur and back on to see if that works.. best advice tho’ is to get a registered engineer to take a look.. don’t ‘book a service’ as suggested though as the visiting engineer will expect to walk into an appliance that’s working and won’t have the allowed time to diagnose and fix the fault and the service. If your car breaks down you don’t book it in for a service do you.. you get it fixed. Don’t keep secrets, give the visiting engineer as much info as possible..
Chaffateux don’t exist anymore and were bought up by Ariston who immediately ceased all production of Chaffateaux boilers, expect to pay a lot of money for off the shelf new parts.. The SE never was a good boiler with multiple issues rearing their ugly head from undersized pumps to brittle pressure switches throwing up crazy fault codes, expensive pcb’s etcs, it’s a 15year old plus workhorse combi so spending anything more than £100 on parts plus labour is throwing good money after bad because after it’s fixed you’ll still have what is still a very old boiler.
I used to work for a local authority who had at least 3000 SE’s fitted and when one breaks down these days they just replace it..