40 is obtainable, but it's even above what Oxbridge usually asks for most subjects. 32-38 is a respectable score and, when you look at the figures, doesn't require that much work if you pick the right subjects. Universities like UCL, Durham, Bristol, York, Exeter, Warwick, Leicester, Manchester, Birmingham, Newcastle and KCL all fall within this grade group.
I'd say that the IB doesn't require any more work than A-levels unless you pick two sciences and mathematics at HL, but it does require more dedication and organisation to go along with it. You're going to have to manage time and do independent research a lot more than A-level students will, but that stands you in good stead for university.
On the plus side, I did really enjoy most of my time as an IB student, the one exception being when I was clinically depressed during my computer science dossier's final week.