The question that comes to mind is, is it more the job or Manchester? By which I mean that if moving to Manchester is a source of unhappiness, then switching jobs may mitigate the issue a bit, but won't solve the whole problem. Of course, Manchester may be fine, but I only bring it up because it is at the head of your post, and it is presented as something about which you did not have a choice and things about which we have no choice can be sources of unhappiness.

Good luck.