I reckon you have at least 2 options. Option 1 A stand alone system that doesn't require a PC to be up and running 24/7. Or Option 2 a system that does require a PC running 24/7. Both types of systems have pros and cons.
For Option 1 look at the Loxone Miniserver, this can be expanded, their head of UK operations is also a member of these forums. The main unit can be expanded with various other bits. It has a built in web server and has free apps for iOS and Android control.
For Option 2 Idratek is worth looking at, it even has its own sub forum on here.
As I said both have pros and cons, and at the end of the day some people like one or the other, I actually like both. And if I was to redo my house from scratch again then I would choose one of the above systems. Though I do prefer a stand alone non PC based system. But if a windows PC is only running one or two programs and is properly maintained they tend not to crash.
I currently have an x10 based system using the Homevision Controller.