Yours isn't the 180 bhp model and it's actually reading low due to the hot conditions, is it ?
My standard 150 bhp AGU (apart from a full milltek) ran 148 at JBS (Mid April.. coolish conditions) and 163 at surrey rr, (Late March, fairly hot) JBS is supposedly deadly accurate and other cars, Wilko/R1GTI, were running down, I think because of the heat, (at the surrey RR day). James (@ JBS) said the full milltek is not holding enough pressure so your turbo can't supply enough boost to give the power, of course, a remap is what's needed. The surrey rr.. who knows ! probably a different setup on different days on different rolling roads. I reckon it's probably somewhere between 163 and 148.. so 155 ish.
Might be a good idea to go back after getting it checked over and ask them to run the same settings.. nowt like another run for comparison, I guess ?!?!