RE; purchase of catalytic converter and lambda sensor?

Hello try here for less than £60.00
http://www.cats4less.co.uk/home.php
Not sure if you will need both though.
Try cat first.
Are you getting smell like rotten eggs if so probably cat has gone.
Be carefull though. I was an MOT tester until very recently when the cars used to fail cat test most of the time it was nothing more than a leaking exhaust. It only needs a small leak in the right place to throw the readings out.

chris
December 2005