pepper / Chilli plants

Could be they are not getting pollinated. You can do this by hand with a small paint brush, and see if that works.

Do as I do with my tomatoes – when the flower opens tap the stem fairly hard – this also helps to pollinate them – or hire a bee – they are very cheap? This time of year and are good workers – Ken

Hi Sarahgibbs
Where are the plants in a glasshouse or poly structure or in the open?
Best grown protected in the UK to get good edible fruit
Ken and Wohlibuli are correct about the polination as this will help but in addition keep them moist and feed with a balanced N;P;K fertilizer
Depending upon the part of the UK you are in then maybe the night temps have been a bit low for early growth and polination but now we saee better and warmer night I am sure there will be some activity soon