Richard, I've lost 2 service fees during my involvement of 20 odd years breeding. Luckily they weren't too large a sum. I think HRA should force studs to offer "Pay on live foal" as the only option. You pay the agistment and working fee when you pick the mare up and the service fee if you get a live foal.
Another issue that annoys me is how a "service fee" used to include impregnating your mare. Now with transported semen they call it a service fee but charge a working fee to impregnate your mare even if you go to the stallions location. It should be called a "semen fee" if it does not include servicing the mare.