In reply to Phil Lyon:
Good dark lenses really can be dramatic - 'cheap' prescription sunglasses can be made by tinting clear lenses into tint baths, which is how they used to do it, but you're really missing out if you go for those. The lenses from the likes of Maui Jim, (get a 2nd mortgage), Oakley and Adidas are breathtaking - try them on on a sunny day and you'll go 'wow!' - they don't simply darken everything, they sharpen vision too.
Some local opticians (NOT the chains) specialise in sports vision, - maybe worth a google or a few phone calls to find out. If you can find someone relatively locally, e.g. who is authorised to provide Adidas, Oakley and a few others, that's likely to be your best though most expensive option - here's an example:
https://bridleopticians.co.uk/sports/
Otherwise RxSports seems the way to go.
PS: Make the most of them - in a few years time your vision will start changing and you will need different correction for distance and near - I've not find a really satisfactory solution for that and I've been looking for 20 years!