I am also an ODP, I have not used Geneva Healthcare but have used Tonix.
The service I have received from them was excellent, I had lengthy discussions on the telephone with the lady from the agency that regularly lasted 45 mins to one hour - the agency called me and they are happy to answer any questions that I have. I have now secured a job through them.
Does your wife scrub as well as do anaesthetics? If so definitely contact Tonix as they can put you in touch with a hospital that lets UK ODPs scrub as well as do anaesthetics which I believe is a rare thing in NZ at the moment.
I can give you a contact name if you wish.