I wish trying to save money wasn't such hard work.
I was going to go with HDEW as they are £1000 cheaper than anywhere else. Hold on, isn't their price too good to be true? Yes. Their website claims:
"HDEW is an online retailer offering superb prices...." but then the small print says, "Please note that by making a purchase on this website you will be acting as the importer of the product for all purposes including all customs regulations,copyright and trademark laws.You accept that the role of HDEW Cameras is limited to sourcing products and making them them available for you to import directly from the country of origin.By purchasing a product through this website you authorise us to make arrangements for clearance of customs on your behalf for the products you have ordered."
So they are a retailer who isn't a retailer. Pfff. A small package might
slip through Customs' vigilant net but a box the size of a 500mm lens? No way.
Next up are ProCameraShop as recommended by Hairy Muff. Spoke to them and had difficulty explaining I was after a Canon 500mm. The bloke seemed to think this was the Sigma 150-500mm
He then couldn't find it on his own website. A bit of online trawling (not trolling) offered a mixed bag of reviews - even one where a 7D was sold by them with a fake serial number as confirmed by Canon. Possible malicious posting but this "saving money" business just wears you down.
So the moral is probably best to pony-up and buy UK stock in the UK - Mifsuds are doing the lens with a free 1.4x TC at the moment. Would only save about £20 on this combo via Digital Rev so I've learned a lesson. Your mileage may vary.
Many thanks to all who replied.