Thanks for the responses so far.
Reason for asking: I need to transport a canoe as a one-off and will be using a 5-door 1-series (not mine). I have a pair of bolt-on roof bars (for another vehicle) and I’m hopeful that it will fit well enough (i.e. not necessarily perfectly) to avoid the faff of having to come up with another solution…
Couldashouldawoulda (or anyone else with the car, tape measure and inclination!): The width measurement is probably the most important and I only need to know to the nearest cm or so to see if my bars will adjust in/out enough to fit. The Thule site lists both 3 and 5 door variants as needing the same bars and foot pack, but I imagine there could be a bit of difference in the widths so it would be helpful to know which you’re measuring.