That isn't really a surprise as a lot of standard K04 engines put down more than the factory quoted 230ps, especially over winter
Stick with stage 1. The (diminishing) returns from Stage 2 and above don't justify the cost of the supporting hardware in my experience. Put the money into handling and braking instead.
Sports cats are crap unless they are massive, most barely scrape through the MOT in year 1 and 2, and then just flat out fail. Nothing compares to the OEM cats in terms of MOT passing, unless you know some dodgy back street garage who will stick the O2 probe up a 1.0 Fiesta's pipe instead of your car's for that part of the test