Furred up pipes

I've just (finally) cleared a problem with my central heating system - the problem was that the pipe from the header tank was so furred up with limescale that the system was not re-filling. As water expanded, it was being ejected out of system overflow and top of system was left dry when things cooled down.

During the pipe cutting etc., I noticed that the 15 mm pipe that I removed was blocked completely, and the 22 mm pipe was reduced to the diameter of less than the 15 mm, all caused by (at least looked like to me) limescale.

My concern is that this is the gunge that I found, but how many more pipes through the system are furred up and on there way to becoming completely blocked over the next few months.

The question is, what can I do about it. I'm presuming that the standard Fernox Protector treatment is OK for preventing the limescale build up, but is there a more powerful (dangerous??) treatment that will remove the stuff that may have already built up in other parts of the system?

For info, the removed pipes were horizontal pipes at the top of the system, between the header tank feed and the pump - don't know if this has any significant as regards limescale build up.

Any suggestions gratefully received.

cut out all the parts of the pipe what u would consider to be very blocked, most of the time the scale will only block the cold feed from the header tank down to where it meets the system, add some scale remover, make sure u drain down some of the system, dont just add it into the tank, lever for a a coulpe of weeks or whatever it says on the tub, just make sure u drain all the dirty water bk out