Yes I have.
Had been D for 35 years at the time, and can honestly say - although I understood the principles of carb counting and dose adjustment before I went, and was doing it up to a point - it was the best 4 days of my life I have ever spent, for my diabetes for starters and for seconders, met some brill people and in between all the seriousness of what we were learning, we had an absolute scream. You know - Fun !
We got a lot of 1 to 1 with the DSNs and dietician and there isn't anything you can't ask them - and of course others also ask Qs and you learn from them and also the answers they get too. I came away with several new friends, amongst them 2 DSNs and a dietician LOL
The best thing about BERTIE as opposed to DAFNE, is that you learn summat, go away for a week and put it into practice, then reconvene next week with your results, which are discussed. And then of course, you learn where you went wrong or what tweaks you can try. Whereas they cram DAFNE into one week solid which is a bit too intensive all at once for me.
It's ACE.