a) fit isolation valves for built in cisterns in such a manner that a stubby screwdriver is no use as the handle fouls the tank, but that if you use the longer one so that the shaft JUST clears the tank, it is too long to fit between the valve and the front of the unit. At least I didn't drop the ratchet screwdriver / socket arrangement I rigged up to get to it.
b) if wiring a 12V downlighter from above prior to the loft being converted, make sure the spur feeding the transformer is about 1 inch too short to reach the hole in the ceiling so that if the transformer fails the owner has faff with at an angle through the hole to get to it.
There's no such thing as a 10 minute job
![Sad :(](./images/smilies/icon_e_sad.gif)
Paul