Nowadays few people will look at you for a PhD without an MSc first anyway, unless you have lots of relevant industrial experience instead.
But, a relevant MSc to the area you'd like to work in can certainly open a lot of doors.
Frankly PhDs! - looks great on your business card, makes it possible to work in a university, little bit of street cred, but not something to do as a career-enhancer otherwise. I did mine because I wanted to do the research, and I don't think that there's another good reason unless you desperately want to be a university lecturer.
That said, the going rate for a PhD studentship at the moment is about £12,500 tax-free, which although hardly generous, isn't too bad, particularly since you can still live like a student.
G