Dear Roy,
Please forgive the familiarity, only I am afraid I don’t know your surname. thank you so much for repairing my barometer! it has been in my family for such a long time and I am delighted to have it back in working order as it its so much more reliable than the weather forecast. A little note such as this is not enough to tell you how happy I am to see it working again, as it seems like an old friend who has been given a new lease of life! So very many thanks.
With kind regards and much appreciation,