On 29/11/2014 00:07, Dave Plowman (News) wrote:

Are you certain you're not confusing it with the residual heat function?

Did you have this on your car?

Something which could retain a reasonable amount of heat overnight would
likely be very large. So where was it fitted?

There's quite a few hits on t'interweb for "bmw latent heat store",
which is described as an option. Possibly latent heat accumulator.