… we highly appreciate the long-standing and close co-operation we have established with you.

….as we're very satisfied with your work up until now, we would very much like to continue using you for our translation work.

....thank you very much for your hard work! As always, it now reads much better.

Thank you very much for always being willing to help us out and for thinking about the texts you're translating – it's a pleasure to work with you.

As we're very happy with the translations you've done for us so far, we would very much like to continue using you.

Thank you very much for your work and for the – as always – fantastic cooperation.