I find the ring circuits ridiculous. I never appreciated Belgian electricity systems, untill I met all of you in this forum! We have standard a minimum of 40A monophase and we can easily get up to 400V 3 phase 40A.
A note abbout 20A radials: 20A can only be used with 2.5 mm2 and with a MCB. A fuse would be 16A.

Personaly I would have appreciated better a TN system than a TT system.