Nightingale in South West Leicestershire

Hello everyone 

I must say as a newbie identifying where/how to post doesn’t appear easy! 
Hope I’m in the right place!  
We’ve had a bird frequently in recent weeks perched at the top of our wiggly willow tree and from my very limited knowledge through the binoculars and a look at our RSPB bird guide we really think it could be a nightingale. Yet is this remotely possible? The small map in our guide suggests just about possible yet internet searches leave me less convinced.

Any thoughts at all everyone! 
Thank you!