As Dig points out curent Brit prices favor the O/U, sometimes by a horrifying margin: (All prices in 1'000 GBP)

SxS O/U
DMcKB 26 33
Boss 55 75
Holland 49.530 60.375

I do wonder why H&H price at such a granular level. Knowing them, I'd bet you could bargain the 375GBP off the price of a Royal O/U if you asked REALLY nicely