Hi Ruth
I looked at two harnesses that had best reviews. The one that was more expensive looked better so I selected it. The problem is that they have "reference dogs" instead of measurments. There was one Staffy in the revies and lots of Spanniers. Size Large is for Border Terrier...but it must be Border Collie. The extra large is for a Labrador. If I check size data for dogs they are larger (longer) and heavier...
https://www.amazon.co.uk/gp/product/B00URW5CTU/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
Harness 2 (doesn't look as nice but have good reviews)
The other harness is in the same serier as the lead:
https://www.amazon.co.uk/gp/product/B016IDJEEK/ref=pd_sim_199_10?ie=UTF8&psc=1&refRID=ETEGE4D46R5545PGWR75
I think its hard to know as Labrador (XL size) so much heavier and longer. Can he really be that big???
If the first harness doesn't fit Lenni, maybe you have a friend with a dog who would pay you a little sum for it as well...
The good thing with the harness is that it has reflection bands for visibility. They also have this "front ring" which should reduce the pulling affect....
Tomorrow you will get your own harness
https://www.amazon.co.uk/gp/product/B0107S039C/ref=oh_aui_detailpage_o00_s00?ie=UTF8&th=1
My ideas is NOT to remove your lovely pull instinct but to make you visible so no car will hit you...