Thanks Mark for the response.  
  
I installed the Scorpion cat-back exhaust yesterday. 
  
I am thinking either stock cats or berk high flow cats? Are they worth the £450-500 they seem to sell for, online? 
  
The only reason I dont want de-cats is I want the car to be road legal / MOT passable. I take it Berk HFC ARE Emissions legal? 
  
I take it the Motordyne 5/16" is probably the better one to go for? I take it a general greese monkey mechanic would be able to fit this with no problems too? lol. 
  
Do yourselves SELL and/or fit the common bolt on modifications I previously mentioned (Plenum Spacer, XYZ Pipe and HFC) 
Is the XYZ proven to give any considerable gain over standard as I dont want to spend too much money for very little returns. More after bang for buck? 
  
Cheers Mark.