What benefits do you get when it's fulfilled by Amazon?
The main two benefits from my perspective being:
(1) Amazon physically have the stock in the UK ready to ship, and will handle the shipping, so you can get it next day if needed.
(2) If you do have an issue, Amazon will manage the return process as well as the refund if needed.
I've bought quite a few YN-622 and various YN flashes from Amazon on this basis in the past few weeks - all smooth deliveries, apart from one issue where the seller had put the wrong barcode on an item they shipped to Amazon - so rather than get a YN-565 flash, I got a crappy wind speed monitor with a YN-565 barcode attached!
Amazon handled the return and refund very quickly at at no cost to me in terms of postage, so I'm quite happy. I'm not sure I would have got the same from an ebay supplier.
I should just add, the supplier that mis-labelled the item as NOT buysku ltd, who are seller of the items currently fulfilled by amazon on the link above - I did buy from buysku and their stuff arrived just fine.