Hi and welcome to the forum narbles.
I was looking for a 130i last year for a daily, but they seem to fetch strong money so I ended up with an E90 330i instead that uses the same N52 engine as the 130i - and the Z4 Coupe.
And after over 5 years of 3.0Si Coupe ownership IMO they definitely feel more special to drive than a 330i - or probably a 130i!
Sadly I sold my 2nd Coupe last week, but only because I've recently bought an M coupe.
Not too many Coupes came to the UK so you need to be prepared to travel, unless you get lucky. The buyer of mine came from South Wales to Berkshire!
And you need to decide which model you want. More of them are Sport models that have the M-Sport seats as standard, but there are SE models as well and some of them had the M-Sport seats as an option. But the M-Sport seats are just so much better, to the extent that used ones sell for around £800 a pair so I'd look for a car that already had them.
I've not read about rust issues on the Roadsters, but they can suffer from roof motors getting drowned in water from the roof drains - although there are a few people who can often revive dead motors and relocate them into the boot out of harm's way for sensible money. Even if the motor works, it's worth getting it moved so you avoid future problems.
But both Roadsters and Coupes can suffer from corroded rear brake pipes - my last Coupe had advisories for them in 2015 and 2016 so I got them replaced in copper. Coupes can also suffer from corrosion on the tailgate - when you open it check around all of the edges.
BMW were a bit miserly with the equipment levels on the Z4s, although all 3 litre models got electric seat adjustment with driver's memory. But heated seats, Bi-Xenon headlights, rear parking sensors, Multi Function Steering Wheel, cruise control, cup-holders and power-fold mirrors were all on the options list. Of those cruise is probably the easiest to retro-fit.
Anyway if any of those are "must-haves" you need to take that into account when you are searching, so happy hunting.
