The short answer to this is no, you cannot. There is a very good reason why you should not go anywhere near your boiler to try and fix it; it runs on natural gas. Natural gas in a controlled burning environment, like the boiler or gas hob or oven, is fine. It’s regulated and measured. If you do something to release it into the wild then a single spark can ignite it and create an explosion. It’s why you can smell gas to tell if there is a leak. Natural gas actually has no scent; it’s an additive so you can tell it’s around by the smell.
If there are any signs of trouble with the boiler don’t delay, call the professionals. Boilers Cheltenham way are covered by the large wide reaching firm HPR. They can soon have any issues fixed or tell you if you need a new one.
Your boiler is full of safety switches and fail safes that will cut the supplier off before anything bad can happen. These are applied (as standard) as per government safety standards. Anything else would mean that they were illegal.
You can make sure that you get regular servicing of the boiler as it will mean that the boiler has all of its parts replaced if they need to be. The other thing that you can do is bleed the radiators. Just make sure you have a suitable towel ready in case they start to leak.