Ok, update ................. finally got round to fitting the Berk HFC's. The Berks fit was spot on and overall it took around 4 hours to complete the job.
The exhaust note is pretty much the same although is marginally louder. There is definitely an increase in noise although if I were honest a little more would have been nice. That said, HFC's do just that i.e. flow more air not delete cats or silencers. May be in the mind but it feels a tad quicker?
I suspect some may say more noise and others it's just enough, either way mine will be staying on!