How do i find where an overflow goes?

Rather than trace the route of the dripping overflow you might consider looking into the places where the pipe might run to.

These may be:

Cold Water storage tank in the loft
Smaller, Central Heating header-tank in the loft
Any toilet cisterns

Lift the lids and look inside - you should easily see which is the culprit.

If you eventually intend to call in a tradesperson to solve the problem then don't bother yourself with all the inspection and clambering about - let the hired-hand do it instead.

Good luck...

Peccavi
September 2009