ive just replaced mine, if its the standard one its all one peice to the cat so you will have to get the center pipe, backbox, u clamp for the center pipe to cat and maybe the back bracket for the backbox as mine was nakered. got it all for £70 and fitted myself easy job. i wouldnt bother with the de-cat on a 1.2 as you will just have to put it back on at mot time or else it will fail the emissions. get a quote of your local motorfactors and online, if they do a higher quality one get that its a better fit.