The Southern Group of Motoring Writers is a regional group that covers the south-east of England, within a line drawn approximately from Southampton to Reading, then to Oxford and encompassing the Norfolk coast.
There are other motoring groups:
Guild of Motoring Writers
https://www.gomw.co.uk/
Midland Group of Motoring Writers
https://mgmw.org.uk/
Northern Group of Motoring Writers
https://ngmw.co.uk/
Scottish Association of Motoring Writers
https://twitter.com/scotscarwriters
Welsh Motoring Writers
http://www.motoringwriters.com/
Western G roup of Motoring Writers
https://www.thewesterngroup.co.uk/