Yes I am happy so far as changes made have been very gradual. By that I mean I didn't just swop her immediately to a different food and less of it. I mixed the two foods (old and new) in different proportions for a while , before getting her on to only the low fat one. Then started reducing the portion size bit by bit to the size recommended by MW which was at the lower end of the guide on the packet for the size she needs to be. I'm using the MW Tracker Mix now (yes it was Farmers before) and now giving her 300g per day split into two meals. This is how MW advised to introduce it in our email exchange. (NB the email from MW came from a different nutrition adviser, not Mark).
Only one person still gives her lots of treats but fortunately she doesn't see them too regularly! I control the rest which she gets for reward based training. People will give her the odd biscuit but it's way less often than before.
Not really much increase in retrieving. We tried to increase the time with the ball on our walks but she just lost interest. She'd rather be sniffing and generally bouncing around. She only seems to enjoy the ball when there are other dogs involved in the game. We do play with other dogs a couple of days a week but not every day.
Her kong fillings are healthier now, that's the other change.
The vet said to expect it to take a long time. He also said that food adjustments are made very gradually so that she hardly notices the difference. She's not an obese dog, just a bit overweight, which I guess is why both I and the vet don't feel the need to 'crash diet' her, but we do want her to lose this bit of weight sensibly while she's still young and active.
Apart from what the scales show her waist is looking more defined now so I'm happy it's going in the right direction.