Beware - there seems to be a problem with the markings on some Avent bottles being about 10% out.
The old double marked 260ml bottles (which show millilitres and UK fluid ounces) are printed differently to the newer triple marked ones (which show millilitres, UK fluid ounces and US fluid ounces). In other words if you fill them up to the right mark for 7 UK fl oz of water, the double marked bottles take about 210ml but the triple marked bottles take about 195ml. I think this means that babies fed with the double marked bottles would be getting their formula about 10% too concentrated.
Avent say that all the bottles are within the EU standard for baby bottles, but admit that they are different and that the triple marked ones are closer to the ideal. They said that the bottles are not meant to be measuring devices which is a bit worrying. What else are you meant to measure feeds up with?!? Although customer services were pretty useless (rude, unresponsive, cut me off, website crashes when posting comments) they will send replacement bottles.