I don't think I would be happy with those O2 readings. Way too slow in changing I would say. I could do a video of mine for comparison (same reader). That said, was the car warmed up when you filmed that - ideally having just been out for a run, or if not then at least up to temperature, and revs held at 2k or so.
Also, have you checked the 12V heater coil is getting power OK? It is fed from a yellow relay on the passenger side bulkhead area. Also have you tried just running with the O2 disconnected? The car will run fine that way, just wouldn't pass and MOT for emissions. If I disconnect mine I can't really tell I've done it.