I will be doing a lot more miles from January, so will be covering about 20 - 22k each year most probably.

Thinking of changing my FL2 SD4 auto for an Evoque Ingenium auto with the Active Driveline.

However, I cannot find anything meaningful about real-world mpg gains or possible mpg.

At £675 it would need to add something useful to the "regular" efficiency of the Ingenium engine, even over 3 years.

Does anyone have any experience with this option?

I reckon I might get close to 40 mpg in the FL2 since it will be motorway commuting but what could I get with an Evoque fitted with this option?

"Active driveline" is just the deactivation of the driveline between the front drive transmission to the rear axle. So when there is not call for rear traction the whole driveline to the rear is disengaged.
Really it's just an efficiency measure so if that is important for you and you want to spend £675 then it's your choice.
You need to remember that with this system its truly is a 2wd when this system is functioning whereas the normal system still retains some drive to rear wheels even when traction is not called for.
Your choice but for me it's a bit of a contradiction in buying a AWD style vehicle. MY15
Tyre Pressure Monitoring System (TPMS)
Surround Camera System
InControl Apps soon to be replaced with CarPlay (WIP)
Meridian Premium Surround Sound
Digital Audio Broadcast
Timed Climate
Cruise ECO Data
Follow Me Home Reverse
Extra Features Menu
Picture In Motion
4x4i screen (WIP)
Digital Broadcast TV
Meridian Rear Media with WIFI
Factory Powered Tailgate
Blind Spot Monitoring (BSM)
Reverse Cross Traffic Alert (RCTA)
Electrochromatic Wing Mirrors (WIP)

Thank you, I agree with your views but want to know if anyone has this and what if any efficiency savings may be gained.

Our FL2 will happily return over 44mpg, with its Alive Tuning remap