Still hunting around and I think I finally found out the parts for them and confirmation that some do dim.
It appears that these do not dim:
The dimming ones are
51168041951 left fold-in heated memory (dim)
51168041952 right fold-in heated memory (dim)
Very expensive but the question is will it work if mine originally weren't dimming, except for the interior rear view mirror which automatically does?
Found this as an example http://www.ebay.co.uk/itm/OEM-BMW-M1...item19d7dbf9c1
but says not to use without dimming option.