Ah you poor thing, sounds very tough.
Firstly, a year ago when she started to insist on you being there it wasn't for no reason - it was for a reason you don't yet know, and one she might not be able to articulate.
How do you feel about cosleeping generally? My 7.5yo shares with me, and we love it. (apart from the duvet stealing - she's bad for that!) Different to you because she will go to sleep on her own at her dad's, or with a babysitter. She much prefers me though - and who can blame her, who doesn't want a mummy snuggle?
The GP is probably right that being tough will stop her. I don't call that tough love though, just tough. And you know what, if you need the space back, I won't judge you. But it's not what I would do.
She has a big change coming up, with overnights with your mother, and she's already anxious. But she's also 8 - she's old enough to talk to.
I'd tell her that you love her, and you can see that she feels she needs you at night. I would explain the shifts you have - and at 8, I'd also explain that work if necessary - for money, but also because you've trained for your new career and you want to do it. I'd tell her that you need some time to yourself to do boring things like housework, but also to have fun so that you can be relaxed and happy. Involve her in the solution. Tell her that during this transition period of overnights with grandma, she'll be in with you on other nights, no pressure to move rooms. Involve her in the solution. Hopefully she'll suggest you cuddle her for 10 minutes (etc) or you can suggest it. Explain to her that you need to find a way to keep her in with you that works for both of you.
And when you wake up in the morning and your nose is buried in her hair, and she rolls in for a cuddle in her sleep, and you get to hear the first thought coming out of her head as she wakes, remember that cosleeping has it's upsides too 
I would try to compromise by taking the pressure off both of you to move her out - tell her you won't even talk about it again until after Xmas. But the payoff is she needs to compromise on you not going to bed at the same time.
I'd also go back to the GP but not focus on the sleeping arrangements but on the anxiety.
Good luck 