Microbore is notorious for blocking up more easily, before doing much else, I'd disconnect a radiator, and open the valve into a bucket, see what you get out. If no water flowing at all, pipework is blocked and you need to start working your way through the system to see where it is blocked. A solid blockage will not be dissolved by any amount of chemical, only solution usually is to cut the affected section out, and either clean it out or replace with new pipework.
Be aware, the black sludge and water created by corrosion in CH systems is like permanent ink, it will stain and ruin anything it comes into contact with!
Be aware, the black sludge and water created by corrosion in CH systems is like permanent ink, it will stain and ruin anything it comes into contact with!
