Tree sparrows - unless your garden backs on to farmland you're fairly unlikely to get them, so in the majority of cases it's perhaps fair to assume it's a house sparrow. Tree sparrows are best told by their all brown crowns and black cheek spot. Male house sparrows have a grey crown and lack the cheek spot. Both sexes of tree sparrow are alike, unlike house sparrows, in which the female lacks the markings of the male.
Tree sparrow -
http://borrowingtrouble.files.wordpress.com/2009/09/tree-sparrow-vrabec-polni-11.jpg
House sparrow m -
http://www.bbc.co.uk/southyorkshire/content/images/2006/01/20/house_sparrow_nigel_blake_470x365.jpg
House sparrow f -
http://www.probertencyclopaedia.com/photolib/birds/Female House Sparrow.jpg
Dunnock - The dunnock looks superficially similar to a female house sparrow in colour, but often skulks around undergrowth in a very un-sparrowlike way, almost like a small mammal. It also has a much greyer head. You also see it has a narrow insect-eater's bill rather than a chunky seed-eater's bill like a sparrow or finch.
http://upload.wikimedia.org/wikipedia/commons/1/1c/Dunnock.jpg
Female chaffinch - easiest to confuse with female house sparrow, but the white wing bar is diagnostic.
http://upload.wikimedia.org/wikipedia/commons/0/02/Female_Chaffinch_800.jpg
Wren - it's tiny! Has a thin insect-eater's bill, which is proportionately longer than the dunnock's, and has a tiny tail which if often holds cocked when perched.
http://www.wildliferanger.co.uk/users/www.wildliferanger.co.uk/upload/Wren 006.JPG
You may also get blackcap, chiffchaff, goldcrest and brambling at this time of year, but the ones above are the main ones.
I'm also not sure where Epsen's coming from with regards to goldfinches, as both sexes are alike.
EDIT - just realised this is a bit redundant now! Glad the BGBW went OK!