I know very few here in the States that don't expect the balance of the hire fee up-front upon arrival to the venue before they so much as remove a briefcase filled with props from their transport. The majority of contracts is 30-50% up front with balance due PRIOR to performance. It is something we must do given how often this sort of scenario gets played out and worse, how often club owners refuse to pay us our due.
If you have a signed contract you are only as protected as the lawyer you can afford (hopefully yours is better well established and worth the cash than theirs.) Catch is, the sum is typically so trivial that we do not take the situation to court in that the costs out-weigh the prize; sadly, people that play this game are quite aware of this most of the time and that's why they do it; they are confident no one will take any kind of legal action against them.
Over the years there have been some interesting ways of dealing with this other than having client accidentally fall down a set of stairs. One case I'm familiar with involved a dentist that had stiffed both, a magician and the clown at a kids BD Party using more or less this same excuse. Both performers arranged for friends & family to visit this same dentist only to send letters along with partial payment based on the same explanation. . . the one thing they also did was have the letters submitted by a lawyer. . . who just happened to be a magician
All Entertainers face this sort of thing, it's just part of the biz. To fight it helps, but is typically futile unless, as has been suggested, you have a Union or similar group standing behind you that can at least "out" such jerks. I know that a handful of U.S. entertainers have filed small claims suits which do get published in the local papers and as a result, an official public black-mark remains behind when it comes to this contractor and their practice of not living up to a contract. You may not benefit directly, but it certain can bring benefit to other performers who can either avoid business with the jerk completely or generate a more iron-clad agreement that's exceptionally binding.