Hi.
I had a similar problem with my car, failed MOT due to no CATS being present.
The Hawkeye only has one CAT located on the downpipe from the turbo
I replaced the entire 3" exhaust with a new 2.5" Cobra system with 200cell sports CAT or so was meant to believe, CAT it self was really small and on test day, the car failed again.
After some hard driving and some heavy revving it finally passed by the skin of its teeth.
Full exhaust cost me about £700.
Had I known then, I would of gone on ebay, bought a used OEM downpipe which could be picked up for a few quid have it fitted to pass emissions then remove
after.