Do not go for a Stage 3 T3 it has the same exhuast housing as a standard T34 (.48)so your lag will be the same!

A Stage 2 T3 will be plenty (good for over 220bhp) and have no more lag than a standard T3 as it retains the .36 exhaust housing.
By a setup he means you will need to be setup/tuned on the rolling road after fitting your new turbo.