Two of these units are city ones - London Chess League and Manchester Chess Federation. These run the similarly named leagues in these cities and so partly double as counties. This gives them a higher profile than the other units.
The remaining five units are geographical groupings of counties.
The oldest of these is the Southern Counties Chess Union, founded in 1892, and currently having ten county members:-
Berkshire, Buckinghamshire, Cambridgeshire (also members of EACU), Essex, Hertfordshire, Kent, Middlesex, Oxfordshire, Surrey and Sussex.
WECU members Hampshire participate in SCCU junior events.
Its site is the most active and comprehensive of the five county units, and also includes an article "What is the SCCU?" which gives as good a justification for its existence as one could expect to find.
The Midlands Counties Chess Union was founded in 1897 and covers the counties of
Derbyshire, Herefordshire, Leicestershire & Rutland, Lincolnshire, Northamptonshire, Nottinghamshire, Shropshire, Staffordshire, Warwickshire and Worcestershire. The Greater Manchester Chess Association is also affiliated to the MCCU (though Cheshire is Northern!) and play as a county in the MCCU section of county competitions.
The site is regularly updated and informative.
Next to be formed was the Northern Counties Chess Union, in 1899. Its affiliate counties are
Cheshire & North Wales, Cleveland, Cumbria, Durham, Lancashire, Merseyside, Northumberland and Yorkshire. Unlike the other unions this one has allowed a couple of "new counties" into its fold.
The NCCU holds its own club competion as well as county events.
Updating of the site is uneven so that certain information is best gained from elsewhere.
Much younger is the West of England Chess Union (1957). (Site consists of pages within Chess Devon Site)
Cornwall, Devon, Dorset, Gloucestershire, Hampshire, Somerset and Wiltshire are the counties forming this union.
Its site is an up-to-date long single page within the Keverell chess site.
The baby of the Unions is the East Anglian Chess Union (1983) covering Bedfordshire, Cambridgeshire, Norfolk and Suffolk. Huntingdon & Peterborough is also affiliated.