BMW wiring question

Hi folks.

Well, first the good news, the fitting of the euro-type light switch
worked perfectly.

I can now switch on or off the head light.

I have also lightened the BM by a fair amount, since they seem to use
about a squillion cable-ties per inch of cabling.

Now, the question..... I want to wire up two small (35watt) lights,
thru a switch (from an RT) to be feed from one of the "spare" fuses in
the fuse box.

How do I find the output from the fuse box?

I assume I'll have to wire in a relay, have the switch trigger the
relay, to light the lights.

Now, I could butcher a wire which is live when the ignition is switched
on, feed that to the switch for the lights, then down to the relay and
have it powered straight from the battery, but surely there is a more
elegant way of doing it?

regards,
CrazyCam