How can I fix my glowworm boiler ?

How do you mean, no hot air coming out of them?? They give off heat, they do not blow hot air.

I never run my boiler above about 55 deg. they get to hot, and if you have kids around.

IF radiators not getting very hot, they may need bleeding. that is the air taken out. Over time radiators will get air in, due to various factors. you will need a bleed tool, very cheap, and use that to open the valve on each radiator in turn, WHEN COLD. to release air in them. You will then need to make sure that the pressure in your boiler is correct. Use the filling loop if not, (the metal braided pipe, some where near the boiler, with valve) You may even need to fill at times while you are bleeding the radiators, as bleeding them drops the pressure Usually about 1 bar, is normal, cold.
Running too hot, will have your boiler switching off and on, as internal temperature gets too high, drop back, etc. Not good for boiler or you, as will decrease life of boiler.
Maximum temerature might sound good, but is not. About 2/3 rd I find is about right. best for boiler, best for you, temperature of radiators not so high, that it could burn. Steady heat is best, NOT full on then off.

SD
December 2011