OK, back on 246, and this is what I see:
Wireless off
Press WPS for 2 seconds - 2.4 and 5 LEDs illuminate after about 2 seconds, sometimes much more quickly.
2.4 and 5 LEDs go off after 1 second
2.4 and 5 LEDs illuminate, - this time period can range from a couple of seconds to maybe 8 or 9 seconds, before they both go off again (and remain off)
I find that this sequence is reproducible
I'll try to do some tests later this week when I get the time.