Long term I doubt the residual value on a last of the line F10 or early G30 once it is 7-8 years old with 100k on the clock will be much more than £1k.

I think a lot depends on how many miles you do. If you're doing 20-25k a year a 80k G30 will have 130-150k on the clock which tends to be about the point the big bills hit and they're not worth a lot.

On the other hand if you only do 8k a year then a 80k G30 will have 100-110k on the clock which is still quite saleable.

They're both decent cars. M Sport or SE doesn't make a huge difference. On the F10 try and look for xenons and some sort of stereo upgrade (which a lot of the later ones had) as the standard items are a bit rubbish in BMW 5 Series tradition. On both F10 and G30 most of the essentials are standard, however.

Jaguar XF is also worth a look - more of a driver's car than the BMW.

The first question you should ask is do I really need a diesel. The depreciation after 3 years is at the same rate as the older f10 something in the order of £2-3k pa. I would be looking for the highest spec car with service history I could find for my budget. The 5 series BMW are really good cars and high miles with proper history should not be a problem. 10 year old F10s are still looking good and if I where you I would be looking at private sellers. Older diesels for private owners whatever car can be more expensive if anything does go wrong.