Thanks for this.
I ended up buying some wind screen glue (sikaflex 221)
and a bunch of assorted rubber plugs like this:
https://www.ebay.co.uk/itm/164771305150
I will install one that fits the tightest and smother everything in sikaflex.
When i had my octavia 1.9tdi i glued my rear spoiler on with this and it took 3 grown men to remove it
so it should outlast the car