I havent tried the Tesco ones and not sure I would unless it was an emergency and I had no shakes to hand.
I HAVE subsituted the Exante bars with Biggest Loser ones as Exante (rather foolishly) said they were ok to use as a replacement to the Exante ones.
I have one BL bar a day with 2 shakes and have remained in ketosis and as youll see from my sig my losses havent been affected.