A lot of the sales/marketing decisions made by the Importer (Audi UK) are made on the basis of what the market needs/will buy. In the case of the UK, the overwhelming market decision maker is the fleet/company car market.
So if it doesn't suit fleet buyers due to cost/fleet charges/emissions etc. it's more than likely that mere consumers won't see it in the UK market.
But as things change in time, to refresh sales etc., you'll probably see this combo being introduced. Right now, Audi UK can sell every single variant currently on offer 3 times over.