Thank you -
Yes, I have done obedience work with her in the house, in the garden and when out walking. If there are no distractions she comes straight to me and sits (without now being told!). I pat her, tell her how good she is, and send her off again.
As you surmise - she loses all this when she sees another dog - or she might start to come back and then change her mind. It is pure excitement and delight at being able to rush around (the whippet in her I expect), and even when the other dogs go back to their owners, she still wants to play, until I manage to grab her collar.
She shows the same excitement and delight when either she or the other dog is on the lead - but of course, I can control her then. Actually, where we walk most of the dogs are totally under control, but not on a lead!
She will eliminate off the lead when we are out walking - but not in the garden (as yet)!
No, we do note have a crate. Don't like the idea I'm afraid.
I look forward to your further response - but I might not be able to get back to you until tomorrow, as my husband hads a hospital appointment this afternoon.