Service by non Skoda garage

Hi all

We have a 4 year old Karoq which we are are looking to sell over the next few months. It has been fully serviced by Skoda up until last year and now is due an interim oil change and inspection

Quotes by Skoda are close to 400, other local garages are 100-150.

I don't have a service book with it as it's all online. Apparently some garages other than Skoda have access to this system, does anyone know?

Thanks