Blackcap
Since the 1960s, the number of Eurasian blackcaps that overwinter in the UK has got bigger and bigger. It’s no longer a rare sight to see them in the reserve in the middle of winter. The blackcap (Sylvia atricapilla) is one of the rare species that sings all year round. Listen out for them:
Recording: Blackcap by Alexander Henderson (CC BY-NC-ND 4.0) xeno-canto.org
Southwick Country Park Nature Reserve 
Yes I’ve noticed them on my bird feeders in winter and the female has a brown cap.
I think we might need weekly reports from your bird table Barbara. It sounds like you have quite an ecosystem going there.