
Every Vet can take blood samples to send off to Idexx who do the reliable quantitative progesterone Assay tests. Just make sure to Post them next day guaranteed deliver so you can get results quickly. You can ring the lab.
Personally if I am able to board the bitch with the stud owner I would take the bitch when she is most likely to be first receptive based on female relatives (I have never had a bitch stand before day 11) and wait until the stud and bitch decide the time is right.
I have only ever done premate tests once with a bitch who played silly beggars over being mated as I wanted to ensure I was not over handling/restraining a bitch that wasn't actually ready.