Apologies for necroing this old but useful thread.

My existing WH is only protected by 18mm-width C20 MCB.

May I know:
1) this 18mm MCB is 1P+N, correct?
2) is this 1P+N mcb safe compared to 2P MCB?
3) if I add RCCB, do I use 1P+N or 2P RCCB?

TQVM