Just thought I'd finish this thread off with the responses I've had from TP-LINK. I've exchanged a lot of emails with the Tech support and Sales support and the result is: they only expect 0-10 clients to be used with their SOHO units. Beyond that, TP-Link evidently consider that it is OK for their devices to crash and drop all connections. Seriously, crashing the Access Point is the acceptable behaviour.

With my consultants hat on, TP-LINK just got moved to me "never by this crap" list.

I'm going to feel guilty even dumping this rubbish on someone else through eBay!