Suzuki Club UK

Hi all. I'm having problem with overheating engine. My car is 2004, 1.5 Ignis Sport, and driving it for 30-40 minutes was enough to overheat it.
After about 5-10 minutes of idling, with radiator cap removed, I can see that coolant level is rising slowly, overflowing. With closed cap it takes longer time but eventually starts to pour into reservoir tank and overflow.
I was checking for bubbles and they are not appearing until coolant starts to boil, so I guess it's not a head gasket.
The heater is blowing cold air all the time and I'm guessing it has something to do with lack of circulation.
How could I check it further to know that's causing the problem? Radiator cap sems okay. There are no leaks until coolant overflow.
If I look under the cap, coolant doesn't move at all, even when fan starts working.
Thanks for help in advance!

Sounds like a possible blown headgasket to me.

I would get a sniffer test and compression test done to rule out the headgasket before going any further.

I have a 03 and an 06 Ignis and they both over heat !, the older one isn't blowing coolant out but she cuts out a fair bit when hot, and she has had 3 thermostats in last 3 years ! took the thermostat out of the 06 and she will go further before playing up, but she is blowing the coolant out and there is a bit of a smell to whats coming out despite clean water going in !, also when 06 is hot there is lots of foam in the rad !, mechanic thinks the head may have a crack in it !, hate to be doom and gloom, but if it helps figure your car out !