To all the contributors on here I want to say a huge thank you. The information gleaned from this forum has been invaluable over the last week.
I'm the proud new owner of a 2003 320d sport in estoril blue with 67k miles on the clock. Since picking it up last sunday I've diagnosed a faulty thermostat, both thermostats have now been replaced under warranty, after these were replaced and the engine was running at full temperature I noticed the dreaded misfire at around 2k revs. I removed the swirl flaps today and fitted blanking plates, cleaned the egr valve and map sensor, ensured the breather was the vortex type, replaced some bad looking vacuum hoses and fitted a new reversing sensor too.
I'm happy to say that the car is now running as smooth as silk, no hint of a misfire, and I'm one very happy boy!
So, thank you all again as I would never have had the confidence to attempt any of these things without the valuable and detailed information and guides on this site.