Thanks for all your replies guys, very much appreciated as always and your comment Pete about the cracked manifold is quite interesting as I had major major problems with a matter early last year when I just bought the car. Basically the exhaust required replacing after I scraped the underside over a vicious speed bump and since then it went from bad to worse. Car sounded terrible, even with a new CAT (£400) and a few months later I couldn't take it anymore and returned to complain to find the rest of the exhaust was knackered, so another £300 later and I had a complete replacement exhaust but the car still sounded terrible. A few weeks down the line I did some major bitching about it on the moneysavers forums and got a call from Kwik-Fit saying they wanted to fit a complete genuine system for me - they did and the car at last was back to norm although I still had a niggle in the back of my head that it still wasn't sounding as good as it did before the fiasco and this is where I think the manifold may come in to play. I know the risks associated with trying to replace these damn things and as I don't intend on selling the car on or anything I am tempted to use PyroPutty2400 on the entire manifold, heard of a guy that did this and basically saved himself a fortune as his manifold bolt sheered when he tried taking the manifold off, so if it is the manifold I think it might be worth doing this and solving the issue. As I say I'm intending on getting the car fully serviced next month so may ask the mechs to give it a good flushing too for a few pints (if u know what I mean!!)
Thanks again guys
Marko