Dear Rob
Thank you for your correspondence enclosing our Certificate and invoice for testing carried out.
The information file and asset list accompanying it was well laid out and easy to understand.
I would like to take this opportunity to thank you for the efficient and courteous way you carried out the testing with minimal if any disruption to our workshop.
…[we] look forward to doing business with you in the future.
Yours Truly
Keep safe, keep legal, stay insured!