Heater not working

My heater isnt putting out any hot air. the engine is sitting exactly at 90C (where it always sits). Am i looking for a blockage do you think?
Have checked and ive got no signs of the head gasket going (my first horrible thought!) and the cable from the knob to the bottom of the heater is connected (my second thought). could it be somethin in the heater/blower box come off?

im thinkin of flushing it out to see if theres any sh1te in there, thought id ask on here first in case it was somethin more simple...

Wasnt very nice driving back from work last night at 7:30 with no heat, gonna wear my flight suit in there till i resolve the matter lol

had this trouble a few winters back m8, had a new thermostat but didnt help muh so had to have a new heater matrix, involved having the whole dash pulled out, glad i wasnt doing it. its still not gr8 but i need to replae my dials. hope that helps ya a bit

when i work on mk2s i first start by flushing the system out with a hosepipe, then cleaning the valves and a last resort is changing the matrix.

you wanna be checkin your pipes to see whether they are all hot