Thinks you need....
for a T6 you need a DC-DC charger as it has a smart alternator, a VSR won't be suitable.
Leisure battery is whatever size you can fit where you want the battery, I went for a 110ah one from
@travelvolts
Fuse box for your 12v distribution, this is connected to your leisure battery +ve terminal.
I fitted an earthing busbar to make things neater and easier for cable routing, Large cable to vehicle earth point and 12v earth points to the busbar.
EC155 is not required, it has a 12v output and a 240v output but in my opinion separate appliances are a better option.
Speak to
@travelvolts, Martin stocks all the pieces you need.