Hi guys

My '03 Vectra 3.2 failed it's MOT today, due to emissions.
It has had a couple of problems, misfires on 1,3 & 5. I changed the plugs and still showed the faults, 0300, 0301, 0303, 0305 & 0135. Took it in for the MOT this morning, as it has run out and they mentioned that the EML was on. Now have replaced the coil pack this evening as that was what I thought would solve the misfire, but am wondering about the 0135. Have disconnected the battery and all faults have gone, except the light now constantly flashes when trying to read faults, not when engine running.
It still feels a bit lumpy at tickover and wondered what I should try next? The retest is free within 10 days, but if it still fails, then I'm going to have to fork out for another test.
The results on the emissions test were
fast idle test, CO pass, HC pass, Lambda 0.970-1.030 result 2.028 fail.
second fast idle, CO pass, HC pass, Lambda result 1.934 fail.
Can someone please point me in the right area, do I need a new CAT or a Lambda sensor (if so which one)?
Cheers in advance