Ravenheat combi boiler LS80T (Little Star) 3 way valve emergency valve?

I was replacing the low water pressure switch on my ravenheat combi boiler and found it clogged with that magnatite (?) black stuff. The DHW flow switch also doesnt work but checking it shows the actual switch to be OK, it looke likt he 3 way valve may be a problem. As it looks like the system is suffering from deposits is it possible to take the 3 way valve apart for cleaning? Also does anyone know whether you can by replacement parts for the 3 way valve if i find they need to be replaced? If so where from? Finally the emergency release valve is not closing properly so the water levels drop to zero in a matter of hours from refill anyone kow of any tips on how to clear the valve as again it is probably a case of deposits getting stuck in the valve. All in all the general theme is Ravenheat boilers are crap (this one is less than 3 years old) but id appreciate some advice on how to fix it instead of buying a new system.