Exaust Advice

[NUTKIN]

I have a tt new shape soop with standard pipe i want to change it to the style i see everyone with where it comes out slightly at an angle with about a five inch end. I hear everyone going on about decat pipes but i want to make sure what to do. Can i completly decat the exhaust an get a new system fitted or are there other bits i need to get because iv had it decated i know all about MOT rules that dont matter cause i will swap back for the day an where is a good place to go for this to be done i live in brentwood in essex so around this area. How much am i looking at for this to be done. thanks