Sime 80E friendly format boiler

Call British Gas. We are not them. Sorry.

Boilers are inherently dangerous for the average DIY for so many reasons, contact British Gas and have them come back and fix it, tell them it was fine before the "service". They may simply have a control valve shut off.

Could be divertor valve is faulty , stuck in Hot Water mode

google your boiler it comes up with a manual go to page 26 it gives you 5 reasons why it goes to f1

Silver flex hose may be the (correct) filling loop. There may be a valve at each end of it, maybe just one at one end.
Open the single valve slowly and LISTEN for the sound of water entering the system, and LOOK for signs of the pressure gauge rising.
On the dual valve version open the first, then open the second slowly as above. Close both valves when pressure is adequate. Adequate is determined by the specifics of your system, but note that more pressure DOES NOT mean better showers, etc.
It should only take a few seconds to top-up, any longer indicates a significant loss of fluid from the system.

This on Y PLAN SYSTEM ???

1/overheat stat2/ fan 3/ diaphrapm valve 4/micro switch check small rubber or nylon hose at fan for pinhole best of luck

best to apply to any local merchant for a manual will get you one sent through the post best of luck

does it have a little red button on the right hand side of the gas valve? if so you must put the gas valve button in the pilot positon and push it down and hold it, then click the red button {push it down} it will click and look at it keep clicking while holding down the button on the gas valve eventually when the gas gets thru it will light could take several clicks of the ignitor

could it mean circulation alert!!!