525 Touring?

[bespokec]

I need a new estate and have spend months pulling my hair out going through the various options out there
The limitations:
I do lots of cycling so bring a bike with me when I go abroad
We have a (big) dog who seems to still be growing....
I only drive on the w.e and on this European trips - the last 3 years has seen me put under 20K miles on our existing car

So I want something that has lots of space, looks smart, drives well and loves long distance road trips
Never had a diesel before and I guess with my mileage a petrol would make more sense
Budget is £20K max, though 15-17.5K would be ideal

I have gone back on forth on an A6 vs 5 Series vs E Class
Not original I know

Now think I am settled on the 5 series and I love the Look of the M Sport package - but is this sub optimal for big road trips and would a SE be better?
Thinking of the 525 - but very keen to hear if the 530 is the better bet
feedback much appreciated !