Just had a Baxi Combi serviced under warranty by Baxi enginner and he reckons I need to use Sentinel x400 & x100 in the system due to the sludge that was present in the old plumbing to the rads etc.
Got talking to a shop and that reckons these are worth a punt also as BG won't fit new Combi's without them inline
MagnaCleanŽ Professional
MagnaClean TwinTech
Sentinel System Filter
anything else out there that's worth a look?