Firstly there was a common and very easy mistake that was made. He proceeded to ask you what power you expect it to make ... never ever tell him what you expect, he will setup the Rolling Road to give you the figure you desire to let you leave satisfied.
As soon as he said "this car will never make 300" i wouldve taken it straight off the Dyno and went elsewhere, the guy is clearly a tit and has no idea what he is talking about.
Also those figures arent so bad, he only used 6400 on the rev range, a TD05's power will still be climbing right up until the rev limiter.
20degrees isnt so bad, its around 17degrees down here in Greenock at the moment so im assuming Aberdeen cant be far off it, especially with it being indoors.
Take it down to Dastek at Dalgaty Bay. Dastek Rolling Road in a confined room with a massive suction system that doesnt allow the room to heat up. Its around £70quid iirc for a Rolling Road.