VAT rules have changed. There is now little/no advantage to be being based in the Channel Islands.
I have always used Choice and their Own Brand worked well with my Canon. However I'm now using a Laser and, when the time comes, will do the rounds, but will use Choice unless their price is grossly uncompetitive.
Over the years I have used a number of compatible cartridge suppliers, and in the main there wasn't a great deal different between any of them. Choice was a company I supported at one stage, but after a slight ignoring of an email due to a problem I went elsewhere.
I have also tried the local 'refill' shops that seemed to spring into life, but alas most of these in my location have since gone out of business.
Since purchasing my last printer, a Brother DCP-135C, I have obtained all the ink supplies for that printer from eBay, at much cheaper prices than elsewhere. Never had any problems so far,touch wood.
Some people on this forum have previously suggested Tesco branded Jettec.