Any chance of a photo? Alternatively, which plants have you seen them on?

there are a few different types of shiny green beetles in the UK, I would guess at some sort of chafer beetle, but without a photo its pretty difficult.

If the plants affected are rosemary, lavender and some other herbs, it might be Rosemary beetle, info and image below

https://www.rhs.org.uk/advice/profile?PID=555

If they're on mint, then read this

http://www.uksafari.com/mintleaf.htm

If these are not the plants affected, then its something else, so no idea without more information.

The best way to get rid of beetles is remove the food source or use repellent.

Having said all that, I really love those little shiny green ones...