When you need to start with "I know this is probably a stupid question
but..." you probably already know the answer.

I need to install a new bathroom upstairs which, due to a builder
letting us down, I'm going to have to plumb myself although I am going
to get a plumber in to QA the work before running water.

One question. I'm sticking the toliet beside an external wall with
easy access to an existing soil pipe. However the joists in the floor
run parallel to the external wall and there's one tight against the
wall.

I assume this means the soil pipe will have to go through the wall
above the floor level? Will the smaller waste pipes i.e. from the bath
and basin be able to go through the joists - they're about 200mm deep.

thanks

tommy