Interestingly enough I'm just in the process of buying a 5600 from a US ebay user.http://stores.ebay.com/CYBERSHOPS
I have been in touch with this ebay user via email this evening and they sound very professional. The only problem you may have is that they only accept payment from international buyers via www.bidpay.com (not paypal).
The steps I've taken so far are as follows (no hitches as yet, but I'll reserve judgement until the unit is in my hands)
1) Emailed seller, provided them with shipping address for delivery charges
2) Received email from seller quoting two options for UK delivery from USPS: 54.95USD for 10-14 day delivery or 59.95USD for 3-5 days with online tracking
3) Used 'Buy it Now' on the Ebay site
4) Paid via www.bidpay.com
5) Now waiting for confirmation that my payment was successful, when thats done bidpay send a money order to the seller
6) Seller receives money order and dispatches item
My only gripe thus far is the bidpay site, which was good apart from the lack of SSL for entering credit card details. Unfortunately I only noticed this after I'd entered my details
The 5600's on this ebay shop are slight above your price of 250USD but they're well worth it (imo) as they're brand new, boxed and come with the camera card.
I'll keep this thread updated as the transaction progresses. All going according to plan I should be holding a brand new 5600 by this time next week.