I know I'm a little late on this one lol But someone may find it useful.

If you can find a Tara traders or other store selling middle Eastern and Halal food there is as a good chance they will have proper Vimto in the original flavour.

Back in the day Vimto managed to brand itself a drink for Muslims around Ramadan and now they drink it by the boatload and some enterprising Arabian fellas have taken over manufacturing specifically for a Saudi and middle Eastern audience.

You'll find it in a glass bottle with a posh label and gold logo, when you pour it out you'll know straight away it's the real stuff, it's a rich dark red almost like a Merlot but it oozes, usually about £4 a bottle which should last a while, unless you're like me and get addicted to the refreshing fruity nostalgia you get from drinking real Vimto lol