Well I thpught I would update you with how my DD is going. It seems that on day 5 (friday) she cracked it. I was upstairs with DH and she shouted up to us that she had weed in the potty (she had actually pooed!) and then produced something about 4 times in the next hour (to get a chocolate button methinks).
She has been really good this weekend - only 2 accidents yesterday (1 which was my fault as I moved her potty and she couldn't find it, and the second when she couldn't open the living room door to get her potty) and no accidents today. We went on one outing yesterday for about 3 hours and also out today, and no accidents then either. I am not usre whether she holds it whi;st we are out or just doesn't need to go.
Also, yesterday she fell asleep in the car with no nappy on and woke up dry, so today I put her down for her nap without a nappy and she woke up dry again! I am really proud of her!
Tomorrow I think I may approach the subject of using the toilet, which may make things easier when we are out and about.