I *think* you are using it wrong?

I'm based in the Midlands.
So I would enter BHX as the starting airport.
Going to Singapore so I enter SIN as the destination. But I don't mind positioning somewhere else in Europe to find a cheaper flight.

I think, it then finds the cheapest of all the ex-eu originating airports, then adds on the price of the positioning flight from BHX to the ex-eu?

Or have i misunderstood?