I've got a Baxi Solo 50/4 RS wall mounted boiler. I noticed the pilot light was out and tried to relight it. It would light but wouldn't stay on. I suspected the thermocouple so replaced it but no change. When I check the manufacturers instructions it suggests that the Boiler Thermostat may need to be reset. It says it's behind the control box - it isn't! Does anyone have any advice to help?