This fly is about 1cm in length and has patterned wings. I have no idea what it is.
No interactions present.
That looks like the one - thanks. I've never noticed them before but there are plenty of snails in my garden.
Lat/Lng: 50.645182, -2.416441
OS grid ref: SY706829
My house is close to fields and hedgerows, not far from the south coast.