As a post-script to this, my new Bosch Lambdas are now installed - a bit fiddly to use their universal connector to rejoin the OEM harness plug to the wiring for the new sensor - and the car is running better than ever now. It always frustrates me that components wear with a slow decline such that you never really notice until they finally give out and they are replaced. Clearly this original O2 sensors had been sub-optimal for a while, as the car is utterly brilliant again now and the old O2’s are now consigned to the bin. That’s 85 GBP very well spent as far as I am concerned and I think something that everyone should consider when their engines begin to do weird things....
