Anyones guess

Hello!  This cheeky little fellow has been regularly visiting my bird feeder this winter.. I used to think he was a black cap but to be honest I am not sure now.. I think a blackcap is larger perhaps. He is approx the same size as an average bluetit. 
On reading up on it with this photo in front of me I believe it to be a Marsh Tit... heavenly anyway

Oil arrived.. hurrah!