Thank you, greytpups, that's really reassuring to hear. We already have a 9-year-old girl, but she doesn't have a particularly waggy tail, so we've not had to worry about happy tail with her. I must say, I got a bit worried about the possibility when the woman from the adoption charity mentioned it yesterday. On the flip side, I'm really pleased to see that he looks so happy in a home environment and around people in general. Our girl's always been timid around new people, and generally has her tail between her legs - so this is very different! ☺️
Thanks for the link, macoduck, I'll make a note of this link and will add these to the (long) list of items I'll need to buy if the adoption goes ahead.