Well the generic Bosch O2 sensor was purchased and modified as described (it came with a little metal tube for crimping purposes and that made a good platform for soldering) and installed. The old one was pretty hard to get at being on the underside of the exhaust manifold and crowded by the oil filter and many lines and hoses. Eventually we had to chisel off the bottom of the old sensor to fit a
22mm socket over it.We also bored-out the catalyhtic converter as it was plugged and restricting the airflow (and, therefore, efficacy) of the turbo. At first there were big puffs of dark grey smoke when the boost engaged but this has settled down... a CO test/adjustment has been recommended but we'll see how she behaves for a week. The turbo screams like a beast trapped under the hood and the car has power once again...it was a gradual decline until one day we realized that we had trouble getting her over 100km/h.
Thanks all for your ideas (good general soldering tips too!). Blurp