I am not criticising your hourly rate!
The RGE site reckons clients pay ?130 an hour for escorting services. They will take some of that, leaving the escorts with less (probably less than ?100/hour).
?400/24 hours is not very high and $4k (the bottom of their quoted spread for three days) is ?2,500ish, so they'd be taking more than half what they're charging the client.
'Get to Gatwick' = they pay for the flight? If they're buying, that'd mean they have all your identity details...
And once you're there, you either need to enter into the awful (and illegal) 'I'll do x for $y' negotiations or accept whatever he might give you on top.
It's not uncommon for phone numbers to be in nominally different places. As well as virtual fax services (they send faxes to you as emails) there are an awful lot of redirection services, so even an NY number, say, doesn't mean the phone actually rings there.