What bats do I have?

What bats do I have?

Observation - What bats do I have?. Description: I put this bat box up last year as we always see bats throughout the year here on our North London allotment. Yesterday we noticed bat poo, we think. Is it possible to identify the species from it? I measured the length - it varied but 10-13mm and 2-2.2mm

I put this bat box up last year as we always see bats throughout the year here on our North London allotment. Yesterday we noticed bat poo, we think. Is it possible to identify the species from it? I measured the length - it varied but 10-13mm and 2-2.2mm width. Some of the poo had a white tip, something they have eaten?