Likewise here in the US, the law says something to the effect of modifying any steering component is illegal.
Therefore even reaming the taper in a pitman arm to fit a different drag link, or cutting a steering column off the original box to reuse, pretty much anything that is not just bolted on parts from the shelf of the parts store is a no no. I guess you could consider using parts from a different vehicle modifying too....
I say use your best judgment, get a few second opinions and you should be fine, unless the law catches up with you.
