Although a +8 owner, I have driven all 4 series of Roadsters, admittedly only for relatively shorter trips.
I agree with Richard that the Series 1 is the best "driver's" car, the power train with the Getrag gearbox ratios suiting the engine better. The handling seemed somewhat crisper than the Series 2 or 3.
The Series 2 was introduced to try to lower the emissions from the ST220 unit.
I truly cannot remember too much that is different about the Series 3 compared to the Series 2.
The Series 4 is possibly the best car for touring , with a docile motor giving relatively good mpg, (unless provoked, and then you really do need a 5 link rear suspension unless you relish visit hedges frequently , or have super quick reactions and skills) . As commented above the instruments are not to everyone's taste, but you can live with the.
In summary if you only want to go touring then a Series 4, if you want to exploit the handling and enjoy driving the Series 1.
