I used to live in the UK and I always used Boots optometry service. I’d recommend booking yourself in for an eye test and mentioning that you want to try contact lenses, they can check that your eyes are healthy and talk you through how to insert and remove them. You dont need to buy anything through Boots but your eyes are so important I feel like it’s a good idea to get them checked by a professional first. Although actually with covid maybe they don’t do this service any more? Anyway, up to you if you want to do that step- then for buying products I’d recommend visiondirect.co.uk where you can select 0.00 prescription lenses (including acuvue as the poster above suggested - the zero just means there’s no vision correction in the lens, all they do is change the color). I used that website when I was visiting UK last year and had a good experience.