I don't live in the U.K. so I can't help you with price but I'll try to answer your other question.
The Hasselblad will be no magic bullet to help your photographs. If you saw a bunch of photographs mixed together which were shot with your Bronica and a Hasselblad you would not be able to tell me which photographs were shot with which camera.
If fit and finish are important to you then the Hasselblad is a much nicer camera and may be worth the extra money to you. It's kind of like comparing a Toyota to a Lexus. Both are fine cars and will certainly get you to your destination but the Lexus is a bit nicer!
Bronica is no longer being made but Koh's camera in New York still services them. I don't know what's available in the U.K. Of course Hasselblad still services their cameras.
For what it's worth I have owned Bronica S2a, EC, and ETRsi cameras. I now own a Hasselblad 500cm.