I used him before on a previous vehicle, very knowledgeable and reputable. Done plenty of research previously.
I'm still doing some searching on here and other laces, as like you said, it seems quite a big increase. I did question him on whether or not it would put any extra stress on any of the drivetrain components.
They do 3 levels of remapping. Red, Blue, Green, his reply was "Stick to the blue and that will reduce the stress although even our red is well within manufacturers tolerances. Blue gains attached. Blue will give you more power as well as increased fuel economy if driven efficiently. Price is £270"
Cheers fella, this lad is local to me, literally 500 metres down the road.