ok im not a doctor but i am relaying info i was told in the MBU (hospital, by nurses and CHN)
you do not need to sterilise your bottles if you wash them throughly with dishwashing detergent and hot waterr, and a bottle brush. washed bottles should be kept in fridge and rewashed if not used within 24 hrs.
Thats right - if you are using EBM - but if you are using formula, they need sterilising because of the bacteria component.

I steralise until they are 12 months and start going onto cows milk.