Let me know if you find the spread check helps. I never thought to try it, partly because the time 1400-1600 GMT is the busiest trading time for GBPUSD. If there is ever going to be a tight spread its then. You're most likely to see the spread blow out in the middle of the night when everyone is in bed. Of course, that might be when your pending order gets picked up, so I'll wait to see how it goes.

Nice thinking though...