Devil is in the detail and I may well have got this wrong but as I read it even for short haul commuters ( so MAN, GLA, AMS etc) it looks like 12 hours "rest" required between arriving at base using what BA call "personal travel" ( which seems to defined as traveling to base by air) and report for
any duty...there is no mention of a local night or a room being required, just "rest".
In fact to my uneducated eye there appears to be room for some sillyness in the rules as written..for example it looks like you could beat the system by getting up at sparrows dodah to arrive at LHR at 0800, hang around in a coffee bar, not working, watch iPlayer or something all day, and then be legal for a 2000 or later report, OTOH you could sleep in at home till gone midday, fly into LHR arriving at 1900 and be deemed illegal for the same report....
IMHO probably much much more understandably there are more restrictive rules for Long Haul "commuters", even those experiencing a minimal time zone change.
No idea where we are with "punishment"....as yet we are looking at a two month audit. Just a IMHO but hopefully worse that would happen to a transgressor first time round might be a *****ing and a note on file...I wouldn't like to test the system too often though, the rules are in the Ops Manual and I wouldn't like to be the first one up against the wall.