Took it to the garage for the MOT, passed fine. Tyre did manage to pick up two screws on the way there! Ordered two Eagle F1 asymmetric 3's to replace the crappy landsalls which came with the car! So will be running Asy 2s on the rear and the new Asy 3 on the fronts.
Since getting through the mot fine I got the garage to look at the errors. The faulty lamba was apparently the one after the cat, said it's not a huge deal and doesn't need to be sorted straight away (will get it done soon though). He also thinks the knock sensor was just a false ping. Thinking everything was going to be fine he hits me with the ABS sensor fault. Something to do with where the rear drivers side ABS attaches has corroded away, but you can only replace the whole unit (hub?) from renault for £180. Perfect.