Hi Tina, there is a bigger risk of sagging with larger implants as your body simply can’t support them and over time they will sag.
When you have the op done on the NHS you have no say in size as they are doing it for free and for medical reasons, if you had paid for your first op you would have been given much more choice with regards to size and shape.
All implants have a ‘life’ and will have to be changed at some point in the future, depending on your age you may have to have a few ops in your lifetime anyway, I don’t think the NHS covers reops but don’t know for certain