Well regarded. Their UK (and US) change/transformation area is basically the Molten Group which they acquired a couple of years ago to bridgehead into the UK market. Molten had a good reputation. Less structured than Big 4 and probably a bit higher up the food chain in places. To do well there you'll need to be a bit entrepreneurial.
A good second or third bounce firm - not the kind of place which will passport you into something special but if you have a big brand on your CV already they are a good, credible, mid sized firm with very good people in FS and Oil/energy.