Two things to consider regarding purchase from eBAY:
(1) Any price that is too good to be true might be a scammer. This happened to me a yea and a half ago when I tried to buy a Mackie Onyx Satellite for $265 (retail was $339 at the time) and it never was delivered. I recouped the money through PayPal dispute resolution but it took awhile. It is not uncommon for scammers to target gear freakz as the items are high dollar and are easy pickings for them. Stick to a seller with a high feedback rating and with a decent number of transactions under their belt, preferably a member for over a year or two. (30 transactions, 99% feedback or better, member for year or more maybe...)
(2) Some Canadian buyers request that the itme be labeled as worth far less than it actually is for purposes of customs duties. For instance, if you buy a synth for $1,000, but the seller lists it as worth $200 on the customs form to be filled out at time of mailing, you will only be taxed on the value of $200. Just a thought, maybe that works well for US->UK sales as well? It is highly unlikely that the customs officers know the worth of everything that comes in, especially electronics. Alot of a sale price is determined by factors other than make/model, such as age, condition, and relative need of the seller for cash at the time of sale...
Good luck!
-Alex