Not a very good idea to buy DSLRs from Hong Kong, as usually if something goes wrong you have to send it back to them. Canon L lenses are a different matter as they usually come with a worldwide guarantee.
Also if the camera arrives without attracting import duty, then you may have problems if you take it out of the country. In this case such as One Stop Digital save quite a bit of money at your expense.
As for the 5D on Ebay you can almost guarantee this will reach £1500 plus in 5 days time.
If you decide to go the Hong Kong route I can recommend Digital Rev. Have dealt with them on several occasions, always found them to be first class