Gurgling in your radiators is a sign there is air in your system. Extracting this will increase the efficiency of your heating system and keep the cost of your bills down. It’s a process called bleeding and all homeowners will need to do it occasionally.
To check if you need to bleed the radiators turn your heating on and gently feel each radiator (taking care not to scald yourself). If the radiator is cold in patches air is blocking the warm water from running through.
When you have identified which radiators need bleeding turn the heating off and wait for it to cool. Take a radiator key (in some modern radiators you may be able to use a flat head screwdriver), insert the key into the valve at the top of the radiator and turn anti-clockwise whilst holding a rag over the area to catch drips. Air will hiss out and when you see water turn the key quickly clockwise to close the valve.
Check the pressure on your boiler when you have finished bleeding the radiators. Most boilers have a gauge on the front but some will have a digital display with the pressure on it. The pressure gauge should show between 1-2bar of pressure and if it has dropped below this you can fill it up using the lever called the filling loop.
Once you have completed all these steps turn the heating on again and check each radiator. If you have more complicated issues with your heating system contact a professional to avoid causing any costly damage. All gas work needs to be conducted by a Gas Safe Engineer, you can search for a local Cheltenham boiler installation engineer here: https://www.gassaferegister.co.uk/find-an-engineer/.
Do note, if the radiator is cold at the bottom and warm at the top this is a different problem. In this case, sludge has built up in the radiator and needs to be flushed out. This is a job for a professional, as specialist equipment is needed, so you may want to seek advice from a professional, like HPR Plumbing and Heating Services (http://www.hprservicesltd.com).
This is a job that is worth doing after your heating has been off for a while, like over the summer months.