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.
I'm sorry but I don't see this as true far short I sticking the car up in the air and fully inspecting every inch how would you notice something like hoses underneath? It's not possible. I checked it over thoroughly as in m first post the rad went but that coul have happened at any poit tampered with brakes in another issue especially when they are disguised! You can see by the tape it's been there longer than a few days!