The phrase 'affordable roadster' is a relative one in this case, given that even this least expensive sDrive20i variant with 197hp was priced from launch at around £37,000. That's with the paddleshift 8-speed auto gearbox that most Z4s have to have; for this base version, there's also the option of manual transmission if you want to save a fraction and involve yourself in the driving experience a touch more. Around 70% of Z4 buyers are expected to go for this sDrive20i derivative, with the remainder of sales split between the two more powerful auto-only models that make up the rest of the range.
On to rivals that compete directly with this sDrive20i variant. The most obvious competitor to what's on offer here is Audi's TT Roadster in base 40TFSI 194hp guise, which at first glance looks quite a lot cheaper, costing from around £33,500 - around £3,500 less than this directly comparable Z4 sDrive20i. BMW though, thinks that much of that difference would be eradicated if you equipped the Audi to match a Z4's level of spec. Perhaps. We'd be less inclined to consider the other direct option, the Mercedes SLC 200, which offers 184hp and in this form costs around £2,000 less than a Z4 sDrive20i. You might like the Merc if you retain an affection for the kind of metal-folding roof that the Z4 has now rejected. Otherwise though, the SLC's a rather aging design and, in comparison to this BMW, much less practical and somewhat unrewarding to drive.