I had a Powerflow exhaust scratch built some years ago for my S1 RST by Top Gear in St Albans - Beautiful job and praised by MOT man each year. Recently went back for some work on the stainless Magnex system on my MK6/7 RS2000 4x4 - As helpful as ever and I was pleased to see the place being improved by new management.

Have heard it's all down to the fitters/welders skill.

I'd recommend without hesitation.
Cheers, John