My sympathies! In the old days when 23 at LHR had decent aids (ie an ILS) we used to revel in the 27L (or more likely 28L) against 23 landers and we rarely got it wrong (okay I remember once but he's retired now) <img src="smile.gif" border="0">
If it was a really strong southerly, you put them on the respective runways at the same ranges and the 27(8)L traffic always landed first. The next 27(8)L lander was positioned at a range which was 90 degrees to the 23 final approach. That meant it was about 5 miles further out than the 23 lander to allow the 23 traffic to land and vacate before clearing the 27(8)L traffic to land.
Having just re-read the last paragraph, it sounds gobbeldygook - I'm sure other airfields that use cross approaches all the time have their own methods.
Now, 09R departures against 05 landers - that WAS interesting!
P.S. Mine's a Highland Park <img src="smile.gif" border="0">