Premium Mini? Premium vs a Fiat 500 or Citroën C2 perhaps, but still very obviously built to a cost, it's no BMW 535D.
When I was in one a few weeks ago for a look, it didn't seem any more premium than a current Polo and noticeably less so than the A1. Not keen on the big and simplistic instrumentation. One tactile piece felt very cheap, the plastic door opener on the inside door card. It flexed so much in use I was convinced it wouldn't last 100 pulls. Always put the money into the tactile stuff - quality perception rule #1.
What I look for in a car is something that looks fine, can be fun to drive and be refined when you want it to be. Good performance and fuel economy (relative to output), Reasonably priced, access to good levels of discount, well specced and with good residuals. Nothing else in my radar fits all that other than the Polo GTI/GT Blue.
A1 is stingy on equipment levels, levels of discount are low, the dealers are generally tossers, and residuals are about the same as the Polo (GFV about 50% for both). Mini is quite low on equipment, residuals are lower than I'd expect, and it's a bit girly -I'd be wearing a balaclava to drive it. I can get £3700 off a Polo GTI if I take out finance then settle straight away to claim the deposit contribution. £20k RRP car (with a few options and DBP paint) becomes £16300, will be an easy £11500 after 3 years private sale. £133pm depreciation on a £20k car? Not even close on a Mini Cooper or upper end A1.
An extra £15pm will take care of the 3% interest you would've earnt leaving your £16300 in the bank. £148pm for a Polo GTI is looking the logical choice for me.