Chillies are usually self-pollinating but additional assistance whether from wind, insects, bees or artificial pollination (hand pollination) has been shown to improve flower set and increase the peppers yield.
In the UK most chillies are grown in a greenhouse so there is little wind pollination & the number of insects/bees are lower than in the garden so artificial hand pollination will help. Simply use the tip of your finger or a small artist brush to move the pollen from one flower to the next. This is what insects do naturally as they fly from one flower/plant to another carrying the pollen on their bodies.
Chilli flowers are also prone to falling off prematurely and one of the reasons this happens is because pollination has not occurred so hand pollination can help. There are a number of other reasons why chilli pepper flowers fall off prematurely so please take a look at our Growing Advice Section ‘Why are my chilli pepper flowers falling off.’