think I might have got somewhere with mine at last - took it in for a service and for the two (!) outstanding product recalls (throttle cable and brake calipers) and I noticed that on my Vehicle Health Check that there was an item under Engine saying 'requires replacement airbox and software update for cutting out issue'.
I asked the dealer about this - it seems that there is a problem with the standard airbox, there's an actuator thingy that fills a hole when the engine is at idle, but the hole is oval and not quite the right shape for the actuator, so it lets in air and the engine runs too lean and stalls. Needs a new airbox and a software update to match.
They replaced the airbox for me for free, which suggests to me that this is a product recall in the making.
Only had the one commute there and back with it so far, but I tried drifting to a halt at every lights and couldn't get it to stall - hopefully it's fixed