Steam Game Of The Year Edition Problems

[Herman30]

Hi, I've recently bought the Steam version of this game and I decided due to it being on sale to go for the GOTY version. The problem is I can't seem to see the additional skirmish maps etc in game. The game in my Steam library just states the standard edition, when I go to the store page it says I can buy the GOTY edition. I'm currently speaking with Steam support and they've said that I do have the GOTY version and I've followed everything they've asked me to do, verify the integrity game cache, run Steam as administrator etc. Am I missing something? Do the extra missions only appear after completing other missions? Thanking you in advance for anybody who can shed some light onto this.