I had a 2015 F31 320D Touring for about 3 years (automatic 8-speed ZF), and it's been all over Europe (and done a lap or two of the 'Ring).
Averaged 50mpg+ and no lower than 35mpg when chasing Z4s on Welsh, Scottish, National hoons.
I like it so much that I simply bought its bigger-engined (i.e. 2016 335d) sibling when I fancied a change. The 320D (especially in saloon form) should easily be available for <£10k.
If you do look at an auto, and it's on more than 100,000 miles, then check that it's had the auto box serviced...as BMW claim it's 'sealed for life' but of course don't care if it breaks once out of warranty. ZF recommend a 60,000 mile interval for the box. Unfortunately there's not an easy way to see if it's working perfectly as you'd need to drive a few to see if one stands out as better/worse than the others. But the ZF box is generally very reliable.
Ride can be considered harsh on the M-Sport models on 19s/20s, but there are Luxury, SE and other specs with standard suspension, smaller wheels with bigger tyres (17/18s) which work better on rougher roads. I run an 18" set with all-seasons for the winter for the better ride and cheaper tyres.
Spec is important on any of these models, and the sat-nav / hi-fi can be a bit naff if it's the entry-level version, as it's a very basic nav system and small screen. The later LCI models (started late 2015 on some models) are more likely to have the touchscreen uprade and a choice between xenon or LED lights, whereas the pre-LCI modesl (to end of 2015, but depends on exact model) have a halogen or xenon option. You can get seat heating (front and rear), steering wheel heating, sport-auto gearbox mode (paddles and a sportier gearbox map), panoramic sunroof (which is fun if you like the sun, but make sure it works as BMW will only sell you the whole thing if it fails).
My upgrde also means it has the latest iDrive 6 with Apple Carplay integration, so I can use Waze maps instead of the BMW ones...which stopped receiving updates a few years back. The ConnectedDrive service is probably useless too...you might see cars advertised with it as a feature, but BMW have deprecated the 3g SIM service, so only allows a very small amount of data over the remaining 2g service.
Old...
New...
They're identical colours/trim (Estoril Blue with Black Dakota leather and M-Performance Alcantara/Carbon interior trim), but the lighting conditions make the old one look darker/duller.
