Hi peeps,
Please go easy on me - first post!

I've played with the 2p/10p version. I think that part of the problem is that it is very thin, so there is a limitation with the aadvark, and indeed it's weaker that the £1/1p. Except under somewhat extreme inspections this wouldn't normally be a give-away, so for me this wasn't the main problem...
Astonishingly (for Gibson!!!) if the coins were mated and then rubbed between index finger and thumb - as if you were rubbing a mark off one of the faces - you would feel a 'click' as you rubbed back and forth. Basically, it appeared that the 2p had been milled to a fractionally larger diameter than was strictly necessary. For the physicists amongst you (or those who remember their schooldays), it may be differing co-efficients of expansion of the different metals which caused or required this, but it was definitely a give-away under close inspection!
The £1/1p that I have is perfect - a genuinely superb piece of engineering! I did this for one friend who worked in a bank, and after half an hour the only thing she noticed was that the coin was definitely gaffed as it was magnetic. Well...yes...but tell me how that performs the miracle! <smile>
Finally, thank you for the tip about the £2 version. I like performing the trick in the spectators hand, and have had problems in the past in getting a reliable mate every time with the £1/1p, and I've also been keen on some S&S stuff - but with decent props! The larger size should make the S&S stuff very watchable!
Cheers! - Mike