Somewhat of a pain. I'm assuming that you've contacted Sky and they can't help?
I've had similar issues with BT/EE in the past and at one point I had 3 accounts! For some reason merging accounts doesn't seem a thing - at best they will close an existing account, open a new account and then add services to your new account. However it sounds like they couldn't/didn't even do that.
I wonder when you set up your Sky Q you were regarded as completely new customer on their system as you had "cancelled" Sky Stream? I remember when I last renewed my Q subscription I was given the option to continue as a Stream user instead - I suspect in that case I would have remained on the same account. (Maybe it would have been the same as adding/taking away say a Sky Sports sub from the package, even though it's a bit of hardware, on their system?)
Assuming nothing can be done now what I would do is see which account has the earliest end date, (which I'm guessing is the Talk/Broadband?) When you approach renewal time for it see if you can cancel/close that account and then add those services to the other account. The downside is that you may lose some discounts (on the other hand you might gain some!) and depending upon how well you time things you might lose a service for a few hours.
If it is the Talk/Broadband first you might also get a good deal by switching to someone else at renewal then go back to Sky later. You'll just need to do a bit research to see what works out best financially for you. Also bear in mind virtually every ISP will pay towards early termination costs as well so you have quite a few ways to play this.
