Which birds don't migrate for winter?

The back garden is awash with little birds chirping away.
I know nothing about birds apart from these are small and brown.
What could they be?
I expected they'd have gone on a winter holiday by now.

This is a great guide

http://www.rspb.org.uk/wildlife/birdidentifier/form.aspx

Just answer a few question and it will give you pictures and a guide to which bird it might be

I used to work at the RSPB HQ in Sandy Bedfordshire but I'm not very good at identifying them but I am getting better, any photos would be helpful to ID them.

only bird i know that stay here are Robins (i think), Penguins, black birds and maybe magpies crows