I replaced our ceiling downlight halogens with MR16 LEDs and LED transformers about 5 years ago, and they haven't given exactly sterling service (problems with connections, leads, and the bulbs themselves) so I'm looking at replacing them with integrated LEDs. The problem is that with most fittings legally you have to get a sparky to install them, so it would be great to get an idea whether a 2-pin plug (as on the Osram Ledvance) is becoming a standard feature: the LED economics don't look so hot if you have to get a sparky to replace them every time they flunk. The other is hole size: what's the most common size these days? My guess is the devices I buy now will not be available in 3-5 years when I need replacements so the widest choice would be good.