I've got an Alpina and absolutely love it. So few RHD cars were built that I reckon it will appreciate in value. That one's non Lux (no Nav, reduced Leather) and for the price, the mileage is a little high. Still, negotiate a bit and you've got a classic performance car on your hands. There are a few for sale on Pistonheads.
Probably not but Sytner Nottingham is the UK 'home' of Alpina and so there is probably a bit of premium for that. When you think that they haven't (yet...) made an E89 version then these may well become collectors cars in the next few years.