yep, I've done it. Hiring a diamond core bit and a core-drill is the way

Hire for a half-day or less; the actual drilling job should take about 15 minutes.

Thoughts (from experience):

Make sure you measure the pipe (don't laugh)
If you drill a pilot hole then go outside and drill in a cm to minimise breakout. [edit - oops, missed Cris' advice - what he says is true but if you are tight on tolerance you need to make sure both holes are aligned or you won't get a rigid pipe through]
Drill pretty horizontally with a slight drop towards the outside.

If it's just blockwork then, as you drill, you'll find it very easy but don't get cocky as it is possible to hit wall ties - be careful to be braced when you hold the drill as you can get a fair wrench. It won't hurt the bit, just keep going - gently.

When you are done you may be able to line the hole with a bit of rigid tube and fit the flexi hose inside it. Makes a neater finish.

It's an easy job.

HTH