Thanks - I think I may get the X800 and do as you suggest, then get the X400 and leave it in for a few weeks just to be sure.
Not sure how I would add it to the boiler though - can I add to a radiator instead through a bleed valve adapter? That's how I've added inhibitor in the past - drained the system a bit, stuck it through the valve then re-filled - is that right?
Not sure how I would add it to the boiler though - can I add to a radiator instead through a bleed valve adapter? That's how I've added inhibitor in the past - drained the system a bit, stuck it through the valve then re-filled - is that right?