Whats the chances of it clearing a shitted up heater matrix?!?!

Basically the clio i drive to work seemed to have a blocked matrix as there was no heat. Have flushed it out using a jet washer and loads of shit came out

But basically even thou water will go thru it now when u turn the fans on u get a bit of heat then it goes cool again, so im guessing its still semi-blocked.

So would rad flush be good enough 2 clean it?! reason i ask is the very nice french ppl made it so u have to take the whole dash out and other bits 2 get the fookin matrix out

Any other suggestions would also be apreciated