R
Reltub
I have seen rads on a sealed system start to corrode after less than 5 years with no chemical treatment! Thing with a powerflush is they pull all the crap through the boiler and if the hex is of small diameter it gets stuck! IMO manually flushing the rads is far better than any powerflush. All that needs to happen now is the system needs draining and the filter needs cleaning, then it needs filling back up and draining again but leave filling loop open until the water starts to run clear, failing that i'd think about disconnecting the heating pipes to the boiler and getting a wet vac on it to try and pull the crap out. Once it has been cleared i'd recommend manually flushing all the rads then leaving a sludge remover in the system for a few days then flush again and leave filling loop open to remove all the sludge removing chemical then fill back up with some inhibitor. BTW the power flush clearly hasn't worked as the whole point is to have a clean system when completed.
Here you go, has ive also said the heating is not working because of something else other than a blocked hex, possibly a filter blocked or faulty diverter as someone else has already mentioned. You need to get a decent gse to sort it.