The only time you wouldn't be able to visit the land-side Travelex desk is if you arrive via a CDC as they drop you off within the Upper Class Wing area.
Although, even then, until you go though security, you are still technically land-side so I guess once you have dropped your bags and recevied your boarding card, you could ask to through to the normal check-in area using the non-CDC Upper Class Wing entrance, scanning your boarding card to get back into the Upper Class Wing area once you have collected your money [:?]
Regards
Regards
James Mitchell