Thanks Helen, that's something I need to do some reading about, I just found an old thread here on the forum about waiting up to 2 years to reduce the risk of cancer and make sure there's time for full development - wish vets talked more about this!
Tolly's about as dominant as a jelly baby, he just loves everybody and is excitable so I'm sure you're right - was just very taken aback by someone so experienced saying she'd never seen a puppy go for it like that!