Fabia VRS Tech Help

I have 54 Reg Fabia VRS. All going well having had the car for five years.

Over the past few months I've noticed the heating from the blowers is coming out like warm at best no matter how long the car is running. I had thermostat changed today as they thought it was faulty. It appears to have improved slightly but still not what it was - Red Hot like most cars after a long run.

I've done some research but struggling to come up with a sensible answer.

The coolant is flowing pot is warm but the radiator appear cool all the time. The garage think it might be blockage in the pipe. ?

Struggling to get a straight answer - I'd rather not waste money chasing the problem if someone can help first.

PS I ain't very technical- any advice would be great.