To be honest mate I haven't had a proper run with the car yet. I think the garage may have removed the charge pipe for better access when changing the exhaust (although not sure why they'd try from above, it's all below the exhaust manifold) so there's a screeching sound on high boost, like a slight leak. I haven't had time to sort it yet.
I have had the fault code about catalyst efficiency below threshold on bank 1 though so I guess the cat is less restrictive! I only had a quick look at it before taking to the garage but it seemed like pretty decent kit.
I did think about the pipewerx one but since I was keeping the stock center and rear sections I decided to just go for 2.5" rather than 3". Looks like the pipewerx stuff comes with a sleeve fitting rather than a flange so your garage will have to sort something there, and there's still the question of reducing it to fit your stock center and rear sections.
The Pipewerx 3" dp and cat is also £550, the Cobra 2.5" bit I got was £410 if I remember rightly. Since my LCR is mostly the wife's runaround now so she doesn't need the extra horses
Also to be honest I'm already maxing out the injectors so I'd need to be sorting that out before aiming for any power increase. I know of a good few happy Cobra customers though so to go back to your original question I'd say you'd be in good hands there.