Polo MOT failure on exhaust emissions

Hi,

I recently put my 2002 Polo 1.2 in for its MOT. It failed on a couple of points, one of them being the emissions. Before the MOT the car was running fine and there was no indication of an emmissions problem (ie, no Emissions warning light on the dash).

After the MOT, I was driving home and noticed the emissions warning light was on and the car was juddering whilst driving at lower speeds (less so once travelling at 40mph).

When I got home I rang the garage who did the MOT and they told me that was probably due to them having to press the accelerator continuous during the test and that the juddering would clear itself up after a while.

It's a few days later now and the car is still running the same with the warning light still on. They are wanting to charge me £300+ to fix this along with replacing some bushes on the front suspension arms and anti roll bar.

Does this sound reasonable? I've been reading on the forums here that the emissions could be the ignition coils and I can get hold of those for £31 each. Would it be worth me trying this in the hope it fixes the problem or should I bite the bullet and pay the £300+ and let the garage do it?

I'm struggling explaining why the car was running fine before the MOT and then suddenly afterwards is running so bad.

Another thread stated that filling with too much oil could cause this warning light to come on. I did put some oil in just before the test, but the level was still below the maximum indicated on the dip stick.

I'm just concerned of getting ripped off by the garage for some problem that they may have caused whilst they were testing.

Any help or advice would be much appreciated.

Steve.