Over the last week I submitted more than 20 enquiries across various web sites.
SafariNow, I feel, was the most effective in that:
* Information given is concise and easy to decipher (allowing for easy comparisons),
* Responses were received within a reasonable time,
* Payment is totally automated (other sites had me completing hard copy forms and emailing them back).
I will definitely recommend this site (I already have) and use it in future.