Good morning everyone, I am new to this forum. :)
Here is the problem: I am supposed to start a PhD in September. At the same university, with the professor who supervised me while I was writing my MA thesis, on the same topic. He is lovely, but also very demanding, I feel like he would not leave me as free as I'd like in my research. To be honest I feel a bit scared and maybe tired of this specific topic, but I can't tell if it is just a matter of general tiredness. The university is one of the best, and London is beautiful, but I feel like the city is suffocating me. It is way too expensive and chaotic, and I noticed that my partner feels the same. Not to talk about the brexit problem, we are very concerned because we are EU citizens. The only reason we are staying is this PhD, and I am starting to realise that the whole situation is making me feel less enthusiastic about it. The fact that I haven't accepted the offer yet speaks volumes about how unsteady I feel.
So, I found a professor at the university of Edinburgh that would be a perfect supervisor for another project, in the same field, but with a different focus. I don't want to present him with the same research I developed with my current supervisor, it would feel like a betrayal. The problem is that I am afraid that the UoE professor might want to contact him. Or maybe the department might want his reference when I will apply. My current supervisor doesn't know I am having these second thoughts, and I wouldn't want to tell him before I am sure to have a place at UoE.
Both the PhDs would be partially self-funded, so it is not an economic issue.
Should I contact the UoE professor? And then should I go on with the application without giving them my supervisor's contacts?
Thank you for having the patience to read my post!

You will definitely need your MA supervisor's reference for your UoE application, so you have to tell him anyway. If there's risk of the two talking, then it's better he hears it from you. He is unlikely to withdraw the offer, especially if you say it's about the city, not the project.