How I'm driving, or where I'm driving?
This is the immediately obvious question. I don't much mind an insurance company logging the data necessary to assess my driving style (IMO it would save me money). But I most certainly do not want them (or anyone else for that matter) maintaining a log of precisely when and where I drive. For assessing insurance risk, any GPS coords transmited should be processed into a road type classification(*) and the actual coordinates immediately and irretrievably forgotten. With the threat of huge fines and damages if they ever break their promise, because otherwise it's certain that they will.
(*) for example M-way, Urban Dual carriageway, rural unclassified, city centre, ... about a dozen types ought to be all they need for risk assessment. Add the county/metropolitan district if they must, I guess London city centre is a higher risk than Milton Keynes city centre.