I'd ask digitalrev for a price they are known and trusted and will probably be only a couple of quid more. Not saying your find is going to rip you off but it pays to be cautious with a large sum.
I'm pretty sure they already cover you for any import charges in the shipping cost:
http://www.digitalrev.com/help/import-handling-for-non-hong/MTQx
Their UK warranty deal is starting to make ordering a 5D mkiii from them a bit more appealing.
I bought my 60D from procamerashop and had great customer service, quick delivery and when I asked them where the camera was from they didn't give me any BS and told me straight away. They also had a UK support line when I called them up and I bought my 60D around £300 under retail. Overall I am very happy I used them
^^^
Is it too late to cancel?
If so, for next time I use these people for both my 35 and 85G, no complaints...
http://*******.com/index.php/sigma-150-500mm-f5-6-3-apo-dg-os-hsm-for-canon-digital-and-film-slr-cameras.html
So you don't get a warranty? Personally I wouldn't be dropping cash on a new camera without a warranty.