You can get the Ritchey WCS for less than that at £25 or maybe a touch less.
Try AllTerrainSports or MerlinCycles.
I assume many of the lower priced high end ones one's are probably OEM versions.
Advantage I find to the Ritchey is is just sits there and doesn't glare out at you, doesn't look large or out of place on a steel retrobike.
Problem I see with the Orbit MX headset is to get the white you are paying for it over the black version. It's a lot to pay for a colour
Coloured = £40 at Merlin delivered
Black = £28 at Merlin delivered
Scratch that On-One have 'em (white) for £25 delivered http://www.on-one.co.uk/i/q/HSFSOMX/fsa ... set#basket