JARLINK 2 Pack Jewelers Loupe, 30X 60X 90X Illuminated Jewelers Eye Magnifier and Magnifying Glass Loop with UV Black Light and Bright LED Light for Gems, Jewelry, Diamond, Coins, Stamps (Black)

It could work depending on your eyes. I use a jewelers loop with 30x and 60x, and I only use the 60x side. I find that it's easier to see the authentication aspects of cards with that side (especially the wizards micro text). 40x is better than 30x, bit it may still be annoying. I got mine as a combo pack here, but I don't know what's available in the UK. As another commenter showed, the kid microscopes would do everything you need very well for magnification, but they cost more (from what I see in the US) and are less portable. This is a consideration if you are mostly authenticating before making a purchase at an lgs.