Definitve editions "upgrade" question

So i own, seasons 1 - 3 S1 is complete the rest were just combo packs, game has the definitive editon for £15 right now, is it worth the purchase? also i’d have to use the disc from now on if i do get it rather than just a DL game if i do install content off the disc? IE costumes?

The Definitive Edition does not interfere with the rest of your purchased content. I used the disc once and haven’t used it since, and KI still works fine. Lots of special edition content and free access to the Gols/Platinum skin pack for Gargos.