As I said In most newbuilds with a fully pumped system (boiler, cylinder, S-plan, y-plan etc) the SFCU is next to the boiler and the two channel programmer for heating and hot water is normally located next to the boiler. Programmers are normally located in airing cupboards on retrofit systems due to ease. Any system from scratch I would locate the SFCU next to the boiler rather than the cylinder cupboard. I believe gas safe require an isolator next to the boiler. So if you install the SFCU remote from the boiler then you should install an additional isolator next to the boiler...which you wouldn't need if you installed the SFCU next to the boiler.