My MY2020 p250 lives outside in the drive, and it's sometimes unused for a week or more. The battery has never needed charging. I also have another rarely used car which has the maintainer fitted under the bonnet as suggested above. Often plugged in for many weeks at a time (this one lives in a detached unheated garage) with no problem.
I have a Clarke CB09 8amp, charges and maintains batteries up to 160ah. £69. I leave it connected to my MX5 over winter and it works in maintenance mode. Comes with a range of connectors so easy to connect and disconnect via a plug if you use it regularly.
They also do cheaper 4ah one for up to 80ah battery which is what my Evoque takes.
Had it about three years now and still working perfectly.
As said there is loads of room in the Evoque engine bay for it and I just run the 240v cable in the gap between the grill and headlamp allowing the bonnet to fully close.
Hope this helps.
Bit of an update. Got the Noco Genius 5 from Halfords for £58.50.
Impressed with the quality look and feel of the whole thing. Plugged it in and it started doing its thing. Left it overnight and the green LED was indicating that it was fully charged and in maintain mode.
Wife drove it and lo and behold the stop/start was working again!
This hasn't worked for a while now, despite the system being checked and battery being charged overnight by my local indy garage, very strange!
Not counting any chickens yet, will see how it goes and report back any developments.