For own vehicle trackdays the closest driving centre would be Woodbridge. And for driving experiences it would be North Weald Airfield. They host driving experiences in a range of supercars and also run track day based driver training days such as skid control.
The Chelmsford area includes the follwing towns and villages:
Writtle | Danbury | Stock | Great Baddow | Boreham | South Woodham Ferrers | Broomfield | Little Baddow | Galleywood | Sandon | Bicknacre | Pleshey | Chignall Smealy | Moulsham | East Hanningfield | South Hanningfield | Mashbury | Downham | Great Leighs | West Hanningfield | Ramsden Heath | Howe Street | Ford End