Hi and welcome to just answer.
I can sympathise with you on this issue as I am on my second Octavia and they always suffer from road noise.
there are two thing you can do to reduce this further .
firstly remove the conti,s they do produce a lot of road noise especially when partially worn and having a hard compound I replaced mine with good year excellence tyres soft compound good grip but less mileage compromises have to be made .
secondly there can be an adjustment made to the rear radius arms to decrease the camber by 2 degrees this will prolong the tyre life as the tyre will sit flatter on the road and it seems not to affect the handling unless you drive it like you stole it.
most decent fast fit centres will be able to do this providing they have 4 wheel laser alignment with camber adjustment.
If you need any more advice on this please reply.
THANKS IN ADVANCE FOR YOUR FEEDBACK.