The Baur's did continue long after the proper conv was introduced in '86 but sold in very small numbers because of the availability of the conv. They usually had the smaller engines because they weren't available in the conv until later in the e30 lifecycle.
Values would tend to be a good deal lower than an equivalent condition conv. The Baur was a factory "approved" conversion so the quality should be fine but they have a fixed roof frame, a bit like the early Jag XJS Cabrio's, rather than a full conv hood. That may be a plus point in terms of scuttle shake.
If the car is tidy with history, then £2k sounds alright.
Whe I bought my 320i conv, about 4 years ago, the dealer also had a tidy 316i Baur of the same age (but higher mileage) for less than half the price of my (mint) car.