I have been through with both Procius and sterling backcheck.
My personal experienceses gave me the impressions of working with punks.
I found out that 4 times out of 5 "no can't do" worked just fine. You do need to stand your grounds though....
Just an examples of manys: they ask for criminals records from all the countries you resided in the last five years.
If you commute they usually ask for both countries of work and commute, even though is not required.
You just politely explain to them that you never lived in the country of work but they usually do not accept it. If you insist and put them in front of their own contraddiction they will back off. If they do not -"no can't do"- will work.
If not, just start threathening them. I am serious....
They are punks, never saw so much unprofessionalism...
Regards