But in the interests of full disclosure...
People who know far more than me about tyres and wheels tell me that current Run Flat spec models are shipped with EH2 alloy wheels (Extended Hump 2) which is a lip on the outside of the rim that keep a run flat attached in the event of a puncture.
A conventional tyre is, I am told, perfectly safe on a run flat alloy up until the moment of a blow out when the aforementioned lip could make a NRF tyre potentionally more prone to consciously uncoupling itself from your wheel.
Makes no odds to me as my feels are flat spotted, the shape of 50p pieces, near cracking and generally knackered bar my off-side rear so I'm going to get new alloys to go with my new NRF rubber when the time comes since they're shot.
This isn't my opinion, just what I am told and what I've read and I'm sure I know less than many people on here. I would just try to gather some info from maybe a smaller garage, a Mini main dealer, and a few bigger tyre places, and when they tell you something different to what you've heard elsewhere, put it to them.
There are different opinions depending on who you ask, and they can't all be right. But if there is a chance it's less safe, I'd rather know about it and then make my judgement with that in my mind. It's probably a small chance.
But then again, thanks to run flat tyres, Cooper S suspensions, and chronic pot-holed roads I was driving around on a completely cracked alloy for God knows how many months - and that can't have been that safe!
I just wish there was some definitive answer. But at less than 400 sheets for some 17" alloys that don't look like Wolfrace budget specials from places like Wheelbase and such (I don't work for them!) it's not much of a dent to have it looking a bit tasty with something in gun metal grey and to your taste as I find the Mini wheels all look a bit chronic - especially at the ridiculous prices they charge to replace 17" Flames like I have.
So in short, no answers here, but it might be worth consulting a wider field of opinions rather than just saying sling them on. I have read (unvalidated potentially manufactured and elaborated horror stories, admittedly) that if you put conventional rubber on a car made for RFT you need to notify your insurer about it.
Some insurers then ask if they are going on the OEM alloy originally made to take RFT tyres and demand you get a letter from BMW saying this is OK, and BMW say you can run a NRF tyres on the car, but only on a NRF alloy without the EH2 lip.
Like I say - before I get shot down(!) - this is just what I've read, heard and been told and I'm just giving you the "benefit" of my advanced state of confusion on the matter!
But for the sake of 400 snots, I'd buy myself some cheapo but OK-looking after-market alloys.