Allard are experts in diesel tuning, should be able to sort one out http://www.allardmotorcompany.com/
oh yeah.. oops. All skodas look/sound the same to me http://www.jabbasport.com/store/index.php?app=gbu0&ns=prodshow&ref=JSFMIC01 Heard some alright things about jabba sport. http://www.forgemotorsport.co.uk/media/FMSKOFMIC.pdf Forge do them too... even tell you how to fit it yourself Price is going to be around 700-800 quid. Probably some on ebay Just search around on teh net for peoples opinions... im not really best placed to advise you seeing as im N/A FTMFW
I got my pipes off a octavia owner that had crashed his car and trashed the cooler so no need for the pipes. Info here on diy cooler for vrs. http://briskoda.net/octavia-i/200-fmic-fitted/128958/
forge ones are only good for a shade over 300hp, blew the end tanks on my old S3 - when i emailed them about it they said they were only good up to 320/330hp - well thats just no good for anyone lol