Just wanted to say thank you to all who post good advice here. It was really helpful, especially the advice to really consider what the dogs were bred for and the posts about the reality of caring for a tiny puppy.
This meant I didn't bring home an 8 month Springer pup who ran to me with his lead in his mouth and whose owner said was a bit hyper as he hadn't been walked that day or the day before because of the rain. When I took him for a walk he zigzagged up the pavements looking for scents and the owner said the man up the road wanted to train him to be a gun dog but she wanted him to come to family like us. I said let him go to the man.
I resisted buying a puppy from a friend of a friend (a retriever poodle cross) even though DD held one and cried, because we have a busy house with older children, students, shift workers but for some half days there would be nobody here.
We were lucky to be offered the chance to rehome a pair of 5 year old whippets who have been with us for over 2 months now. They're great. They arrived house trained, crate trained, ok on the lead and don't go upstairs.
I don't really like to put pros and cons as they are part of our family now and we just accommodate their ways like we do each other. It feels a bit like writing:
DH - most friendly and affectionate but showing a tendency to grumpiness as he gets older, especially with people he thinks are rude in shops. He can guard the TV remote and can growl if you change channels even when he is sleeping.
Anyway back to the dogs. Remember these are adult whippets not puppies.
Pros
Calm and clean in the house and garden (prefer to poo and pee on walks)
Non destructive
Affectionate
Cheerfully biddable (except when they see a moving cat, see below)
Love a chase and a play but then happy to sleep
Athletic, love to run and jump over puddles and streams like show horses
Will walk for miles or do 20 minute dash around block (we tend to do one quick walk on lead and one off lead over fields/woodland)
Cons
Small furries, especially cats and squirrels (fine with small dogs, even a Pomeranian, jumping and snarling at them) so have to be on lead anywhere near cats as thier recall evaporates
Like to play chase with other dogs and can interpret bouncy young labs who run and jump up as wanting to chase which can surprise dog and the "he's just being friendly" owner (I do recall them unless it's a dog like a young beagle we see who likes a chase)
They have sensitive tummies and can be sensitive to teenage tantrums