I moved my Friesian over in 2012.
The process was more straightforward than moving a cat or a dog, honestly, because you have to use a shipping company and they have to handle everything. We used The Dutta Corporation and were able to do quarantine at the facility we were using in the US.
The cost breakdown and requirements:
Transport from stable to JFK $200
Pre Export quarantine at JFK $200
USDA User fees for monitoring shipment @ $300
USDA User fees endorsing health paper and courier services @ $250
Air freight from JFK landed AMS in a single stall including, professional groom, shipping supplies, customs filing & Tim Dutta fees @ $3,700
Fuel Surcharge @ $400
Horse equipment @ $3.25/ kg with a minimum of 100kgs
Upon arrival into AMS through vet and customs clearance @350 EURO
Transport to Surrey UK including clearance into UK & Layover @ £500 approx
Health requirements:
1. Neg. AGID Coggins within 90 days of shipment temporary export or 30 days for permanent export original to be attached to Health Certificate
2. Vaccination for EEE & WEE not less than 30 days & not more than 180 days within ship date.
3. Horse must have FEI passport or registry papers and a copy to be attached to the health certificate. (Not necessary for permanent export)
4. EVA test within 21 days of export (Stallions only) Negative result with a dilution of 1:4 or negative semen result (if the horse was vaccinated please fill out the date in appropriate column and cross out the one that does not apply.) Please provide a copy of negative EVA result before the horse was vaccinated.
5. If the horse was vaccinated for West Nile Virus it must have been done at least 30 days before export
The total costs were in the $5500 range when all was said and done. There was little to no misery involved -- Dutta Corp handled everything with my vet so apart from packing up my tack trunk, moving him was the easiest part of the move!
My horse moved like a champ, but I also had some knowledge of UK vs US equestrian practices -- feeds are very different, horse keeping practices are not the same (even though we were moving from one FEI facility to another) and if I were to give advice, I would say get acquainted with some yards and owners over in the UK before you decide on moving. I'd spent extensive time at the yard we moved to, which helped.