Is there any reason why you can't ask a family member or a trusted close friend if they could buy New Horizons online on your behalf? They can order NH online for you, you then give them the money (in cash) and wait for the game to be delivered on their doorstep. You then go to them and pick it up. It's as simple as that..........
It's not really Vstep's fault as they don't dictate how many NH should be sent to different shops across the UK and the Europe.
Even the GAME & Gamestation shops near where I live don't have NH in stock either, which is why I ordered my copy online.
Kev