Whoops, looking at my post now, it looks like I'm crowing about 16mm2 vs 10mm2. Of course, I have no idea if it's better than 10mm2 and there's no way of proving it either way unless some people are radical enough to rip out a perfectly good 10mm2 RKR setup and replace with 16mm2. I'd guess what works for who is down to length of cable runs (voltage drop directly proportional to length) and how much current your kit pulls. So I'm sure 6mm is great in the right situation, especially if the runs are short - less than 20% of my runs in your case, Sul.
Mike, yes I think the 16mm might be a first - guess I'm the only guy bonkers enough to try. And Sul, you nailed me bang on - with best part of 20m in the tails and 18m in all the radials (you're right about spurs vs. radials), I didn't want to lie awake at night wondering if I should have gone to 16mm2. Given that 95% of the pain is in the installation, I just couldn't talk myself out of 16mm, althought my sparky tried very hard - sore thumbs etc.
Yes, I do have the full setup with 100A junction boxes with beasts hard-wired into them. I'm using a Memera AD12 with 32A RCBOs. Being a bit nervous about hard-wiring (and giving up my investment in quite pricy mains cables), I ran my installation to allow both hard wiring and 13A unswitched sockets. I did this by putting sockets 6" beneath each 100 junction box, with a short hop of 16mm cable runing from junction box to socket. I was hoping not to hear a big change going from sockets to hard-wired, but there it was big and undeniable, so that was that. My nice silver-plated sockets are now out of circuit and the beasts have taken over my nice branded power cords. More tears, but reality won the day. I knew Roy was right deep down, but it's always hard to turn over your own preconceptions, until you hear the difference.
By the way, I've got some very nice power cords and conditioners if anybody wants them
To be fair to them, they did a great job of patching up a crap mains supply.
Spacey, yes, Roy made a big point about all radial having to be right length. I had to roll each run out in the car park back of my block and measure each one out. I then made sure that if I did any cutting, I took the same amount of each radial (means you have to layout end to end before cutting and think hard before you cut).
Mike, I do plan to put in a dedicated earth - it's just quite a big job for me being on top floor. In the initial install, we put in a new 10mm earth cable all the way from the earth braid of the 3-phase cable head to CU. Not the same as a dedicated earth with its own spikes, I know.
Andy, good to hear you found the same thing as me - I was only really expecting a big change in dynamics, but the change in detail and musicality were every bit as big.