Purchase single stock photos

With the correct subscription, you can buy a single asset for as little as 0.21€+VAT. But you will need to take 750 assets/month subscription. Buying single assets can be done with credit packs. For 40€+VAT, you will get 5 credits, meaning 8€ per asset. Credits expire after one year. You will need to check the GBP prices.

The least expensive option is a 5-image credit pack for $50, which is $10 per image. Alternatively, you can start a free 30-day trial and download up to  10 images. Be careful to cancel the trial before 30 days though, or you're on the hook for an annual plan. You can also look for a suitable image among the Free Assets, though there isn't as much choice there.