I've been a fan of MK rcd's for years, but for some reason they stopped making 100ma S types. My local wholesaler only stock control gear, and I've found their delay types to be awful, particularly when pv inverters are on the circuit. I've just discovered a friend of mine has about 30 meters of tails running under his floor from an exterior cut-out to the cu. No protection whatsoever, TT earth, so as a favour I'm gonna fit a fuse and rcd. Didn't want to spend a fortune though ;-) I would assume that even these cheapies have to meet a certain minimum standard and be fit for purpose?