A friend of mine has just moved into another flat with this boiler having come from one with a Worcester Bosch combi (24kw greenstari I think)...it seems to work fine but he wants to change to WB for no other reason than that's what he knows and prefers. I just said if it's working fine just get it serviced and tested/topped up for inhibitor as the last time it was serviced was 2007, he's going to get a rad moved so is it worth putting in a magna clean or similar while the system is drained down? Thanks.