If you intend to buy bottled water for bottles, check that it doesn’t have a high mineral content and try to use still water that’s low in sodium. Look for ‘Na’ (the chemical symbol for sodium) on the label and choose a bottle of water that has a Na/sodium content of 200mg or less per litre.
Take sterilising tables with you – these can be bought in chemists/pharmacies. Buy a large bottle of water, cut the top off and add the correct number of sterilising tablets for the volume of water. You can use this as a cheap and effective steriliser for 24 hours, after which time you must dispose of it.