It wouldn't be tied to a transaction though would it? Just enough to suggest you may have made a transaction of some kind at that location.
Still, seems like just holding the money may not be enough. Try to swap it. £500 you took out 6 months ago all got spent in the same place, that is probably still your money. If it was £80 of yours, £140 of Johns, £200 of Freds and £80 of Beths, now its far harder to know. Plus its mixed in with so many other transactions as well.
More people swapping notes would also further reduce the value of that kind of surveillance.