Ash is a good guess I think. The bark looks "Ashish" too
I mean it's very light and smooth on younger specimens.
I had one that was beginning to look good, but it died last year. I should have repotted it, the roots can be very strong and invade the pot, which is not good when the temps are high.
At least, we don't seem to have the problem you have in Britain. One of my late uncles lived in New Ash Green : I wonder what this town would called now...
Why don't you mention your location in your profile, country, county, nearest big city, ... ? You don't need to mention your postcode