were is the cheapest place to purchase a cat for my new build?

Most people beg/borrow/steal a Cat for the IVA test and then remove it afterwards. Obv you can buy one and leave it on, just thought I'd mention it...

Surely that dont help things for an MOT in three years time though?

Assuming the engine is newer than 1995 or what ever the cut off date is.

Oh and sorry I dont know where to get a CAT. I know there were posts on here a while back discussing high flow ones for 750mc racing. All of the racing drivers were moaning because its a new requirement.