Hey jim, welcome to the site, i live in lee chapel north, just down the road. without a car or riding on the roads then your pretty limited in basildon.
langdon hills/one tree hill has some good riding, from where you are you can ride the paths through the town, up past the hospital and turn down dry street into one tree hill (quite roads) thats more trail riding though.
i regularly do basildon-shoebury loop (36 miles) but if thats to far then jump on the train to shoebury and ride down to leigh, getting the train back again. nice route down the seafront and into old leigh.
Check out this site for other local routes
http://www.cycle-route.com/routes/Essex-Routes-76.html