Hi Davo,
the thing that would make me stay away from the fuzeblock is that it is not water sealed obviously. Water getting into electrics is no good at all. You could argue that the original one is also not water sealed and that it is basically only a fuse-box replacement with no electronics in it and you are right, however, it is also an issue over here with corrosion on the contacts. To just replace the fuse box however, you could also use something much cheaper...:
Fuse Box
Use two of them for constant and switched power (which is the intention of the fuzeblock) and you are a) way cheaper and b) save space and weight). The only relay in that fuzeblock is just for switching the power on or off, not for turn signals, horn or other components, so you basically need these relays in addition to the fuzeblock. In the M-unit, everything is in that tiny little box. Love it. To achieve the same, you would need both the Sachse twin-relais and the Fuzeblock, which cost you at the end maybe more than the m-unit and is much more complicate to wire and has some other pitfalls.
@Cam: there is an easy fix to the headlight thing: either let the main for the headlight go through the switch on the handle bar (that's anyway how it works on our and all other bikes) or - as you said - use another relais for that which is the better solution. It's 1 m more cable and a 8? relais - so what...
Or benefit from the better visibility when leaving the lights on and invest in a proper charging circuit of your alternator, which is anyway a good idea...

Or reduce the power consumption of the bike by using some LED bulbs on tail-/brake-light, turn signals and parking light. Reduces the need for power by roughly 25 - 30 Watt. Or use the M-Unit to switch between parking light and low beam while using highbeam with a separate switch on your handle bar (which you have anyway...). Or...
"Many roads lead you to Rome" as we say over here
