It sounds like you havnt checked it over well enough i reckon.
In terms of the MOT it wont help you as once it has left the station anything could have been done to it. Proving it was in the same condition during MOT will be difficult if not impossible.

Brake pipes wrapped in tape arent too obvious? Why is the tape on there? It would never stop a leak so you would really have to presume the pipe is visably perished and its hiding something, at which point you proceed to remove the tape for confirmation. You may or may not have had time to do this but its a risk you take buying used cars.