Hi Jonny
To clarify what I meant about level converters ... as well as a 3.3V power supply for the sensors, you also need to translate the two signal connections between 3.3V and 5V.
An easy way to do this is with a ready made converter.
Adafruit do this one: 4-channel I2C-safe Bi-directional Logic Level Converter [BSS138] : ID 757 : $3.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Cheers
Ray