Just to add a slightly different angle to this, I actually believe it is the fault of Rover that this has happened.
Allow me to explain...
Generally (although there are a few exceptions, so please don't feel the need to post pictures that disprove this), cars have the fuel filler cap on the opposite side to the steering wheel; so cars that are designed to be RHD (Japanese cars being the best example) have the fuel filler cap on the same side that the MINI does.
The reason the MINI has it there? Because it was originally designed to be RHD (a point Paul M made recently in another thread).
When the R56 (and subsequently the Clubman) was designed, it was left there, because that's how it has always been, and it was obviously easier to leave it there and work around it.
If the 1st Generation had been designed, from scratch, by BMW, rather than Rover, it would have been designed as LHD (like all BMWs) and the fuel filler cap would have been on the other side.
So, the reason the RHD market has now been "shafted" is because the MINI was designed to be RHD.
By Rover.
So it's their fault!
Of course, this raises the question, had BMW originally designed the 1st Generation MINI as LHD, would they have found a way to put the rear door on the side that it has actually ended up on, or would they have done the reverse of the situation we now have and just stuck it on the other side as the cheaper and easier option?