I'm really unsure of the issues with what people like to call Grey Imports.
I've bought an imported camera (which ALL of them are) before, from a trader on here. I got a UK invoice from him, and a Canon warantee.
Now I've bought a 5Diii from HDEW. I get a 12 month warantee with Canon followed by a further 2 year guarantee with HDEW. UK charger / accessories etc.
The fact is that these items can be purchased in bulk abroad cheaper than in the UK, and some companies take advantage of this to offer better prices. It's not a case of evadfing tax or duty, the import duty rate for digital camera bodies was zero last time I looked. Import VAT is paid at the time of importation, so no evasion there.
So, Canon warantee, cheaper price, and great reviews for HDEW as a company on the internet.