Guy,
I have done US Customs clearance myself, but not specifically at ATL aircargo.

I'm assuming you are doing a "temporary" import of a UK registered bike to use/ride the bike for permitted tourist riding by the registered owner, rather than attempting to do a "permanent" import of the bike to the US. If you're attempting a "permanent" import, forget it--all bets are off and the following does not apply.

If you have the necessary EPA & DOT paperwork, including EPA prior approval
of temporary import by you, the bike owner, then YES, you can "theoretically" go through all the clearance paperwork/ procedures yourself onsite at the ATL airport.

BUT--you must be very clear what that means in terms of the actual, precise set of steps/ agencies/ physical locations and time required to complete all these procedures.

I would suggest you go back to James Cargo, and have them describe to you in precise detail, e.g., the following (including the precise or approximate physical location of each step on a Google Map of the ATL aircargo facility):

1. Which aircargo airline/ carrier will airfreight your bike into ATL aircargo;

2. When is the bike scheduled to arrive; not just date, but flight# and scheduled arrival time at ATL aircargo (James Cargo should be able to give you this detail from the "AWB" (Airway Bill) of the airline; they may even be able to show you how to log onto the airline's aircargo online tracking service to follow/ verify this detail);

3. Where exactly--physical address, name of contact, tel.--the bike will be
un-loaded at ATL. Is this location an office of the aircargo carrier, or a separate ground handling agent contracted to the aircargo carrier ?

4. Is this the same location where US Customs will physically examine the
bike (if they do--they may or may not), or review your EPA & DOT paperwork?:

5. If the bike is physically at one location, but US Customs processes the paperwork at another office location, where? and how do you get from bike location to Customs office location (if different) ?;

6. What is the "normal" paper processing time/ lag between bike cargo arrival and US Customs physical and/ or paperwork review? What are US Customs office hours for this specific kind of temporary vehicle import review?

7. Assuming you get all the above detail in advance from James Cargo, you should be able to "map" where you need to go, step-by-step, and how long the entire process should take, from un-loading the bike to final US Customs
approval. If James Cargo cannot provide all this detail, you need to fill in any detail info blanks to your satisfaction in advance.

8. Don't be surprised, even if all your US Customs/ EPA & DOT paperwork is complete/ accurate, that you may have to "educate" individual Customs agents about the relevant regs & paperwork for "temporary personal vehicle imports," because that type of import is not all that common at ATL--or you may get lucky.

9. You say above that you spoke to "a customs agent in Atlanta." Do you mean she was a US Customs agent, or a customs broker/ agency? They are very different. US Customs personnel/ "agents" have no financial interest, but customs broker "agencies" obviously do. One reason that many folks use a customs broker agency is because the actual time & procedures can be so complicated/ onerous that a broker/ agent may save you considerable time, and that may be worth the fee you would pay them. Also remember that US Customs personnel are used to having cargo cleared by customs broker agencies, rather than by the personal owner of the cargo--so if you attempt this bike clearance personally, it will be a bit unusual/ out of the ordinary for the Customs staff.

9.1. the following webpage of ATL US Customs office(s) contacts might help fill in any blanks/ questions:

http://www.cbp.gov/xp/cgov/toolbox/c...ts/ga/1704.xml

Name: Atlanta Hartsfield/Jackson International Airport
Phone: (404) 765-2300
Fax: (404) 765-2325
Operational Hours: 8:00 AM-10:00 PM(Eastern)
Seven Days A Week (7)

10. Don't forget--depending on how James Cargo (may be required to) prep your bike for flight, i.e. leaving little or no gas in the tank, you may have to find out in advance where the closest petrol station is to ATL aircargo facility, before you can actually ride it onto the highway.

11. Assuming you're doing a return aircargo shipment--eventually--back to Blighty, don't forget you'll have to reverse engineer all the above procedures from wherever that return flight originates

good luck!