Hi Nicky,
Did you sign agreement before your operation that they can perform something else? It may not make much difference to you because they will still do bypass/sleeve later (I understand that you had it paid by NHS?), but if they did it to me, I wouldn't have enough money to try again later and I would not qualify to have it paid on NHS. Why it worries me is that as far as I am aware, the balloons don't have as high success rate as the bands, so I don't want to spend my hard earned money for something that may not work.