So cleaned the Lambda sensor wiring connection (where it hooks to the loom) yesterday with some carb cleaner and WD40, took for a spin and seems to be an improvement...especially in 1st gear and neutral...will now rev out properly.

Other gears still stops at 4K but will respond to a roll off throttle and more forceful roll on, still no joy on full throttle though.

makes me wonder if the lambda is flaky, cheaper thing to swap out (£21) before swapping out the cat.

need to wait for pay day sadly before buying any more bits

Thanks for your help thus far