If I understand the review then it uses a gaffed US coin. I live in Canada and if I did a trick using a US quarter I'm sure people would be suspicious (and US coins circulate freely in Canada). I would guess that using a US coin in the UK would be an immediate tip-off that something is fixed.
Scotch and Soda has become a mini classic of magic, and yes it uses a US coin and a Mexican coin, but for goodness sake don't let that put you off. This isn't an impromptu trick and was never intended to be one. Lets face it you were never going to ask to borrow the Mexican coin even if you live in th US. We are Magicians and as such we use coins because the are bigger and more visible. It's as simple as that. I don't do much coin work myself but my friends that do use half dollars anyway (I'm in the UK btw), just because they can be seen more visibly, especially for a matrix or a Coins across routine.
So don't let the currency put you off.
For something ike cig thru coin, where it IS impromptu and you should ask to borrow the coin first, then yes of course it should be in currency, but not for this.
MagicDiscoMan had it right when he said...
so i painted them green and drew a stick man on one face, now the kids as well as the adults follow the action.
Great magical thinking.