It does appear that a number of hybrid vehicles are affected with 12V batteries that drain relatively quickly, and this is caused in part by less capacious batteries being fitted from the factory.

Toyota recommends that you put the car in 'Ready' mode for 60 minutes at least once a week in order to prevent the 12V from being excessively drained. If this is not a viable option you may wish to consider a trickle charger - we recommend the CTEK MXS charger which we reviewed here: kit.honestjohn.co.uk/reviews/review-ctek-battery-c.../

The CTEK is a trickle charger we would recommend because it has a lot of safety features, comes with a five year warranty and also offers graduated charging, so it reduces the amount of charge fed to the battery depending on its current state.

At present this issue appears to be affecting Toyota customers more than others, but it is important to consider that Toyota has been selling hybrids in the UK for decades so it is likely there are more hybrids on the road from this brand.