You are worth your weight in gold.
Many thanks for all of your help (I couldn't have done it without you!!!). I have recommended you to my partner.
I would like to thank you for the service you provided and the valued support. Thank you again for a very efficient and effective service.
I would like to thank you for all the assistance you have given me and your kindness shown.
I hope you do well, you are relaxed helpful and approachable.
Thanks for all the help.