Howard's one (S/C MX5) looked brilliant, but it was about the same pace as my car - probably slightly quicker.
Now my car could not even consider to keep up with your last Focus ST so I'm not sure how you want to look at it like that.
I haven't kept tabs with Howard's SC'd 5, but iirc it's an M45 conversion which usually adds 30-40% resulting around 160-170bhp unless further work is done. Whilst a very useful amount and great for day to day use it is similar in power to your hatchback and will therefore be similar in a straight line whilst rolling. 220-260bhp is a significant amount of extra power in something that weighs just a tonne.