Flying insect or bat?

Hello, there’s a strange sound that I can hear most nights in my garden, a short and sharp high pitched sound that flies over pretty quickly. It’s in short bursts and repeats every minute or so. I’m pretty sure it’s a bat since the sound goes over quickly, but I don’t know what these sound like. I’ve attached two recordings, one with an annoying helicopter which is slowed down so you can hear it better. Any ideas? 
Thanks