Google it to check but the tommee tippee ones have a line that you can fill water up to and then microwave them to sterilise them. Depends if you have access to a microwave though
Some mam bottles can be sterilised in the microwave too x
Get some Milton tablets, don’t take up any space and you just pop a tablet in a sink/Tupperware full of water and it’s stays sterile for 24 hours x