@Sophie thank you!!! will try this
Not exactly the same but have you tried Dr.Browns? My son transitioned straight away from mam bottles to dr.browns and had them for good 2 years and a bit over as we then used the transitioning bottles! X
We had this issue so made the holes on the size 2 slightly bigger using a sterilised safety pin. We used the modified tests for a week or so then slowly introduced a size 3 teat. It can take a few feeds for them to get used to the new flow