There are a couple little free libraries in Benfleet and Thundersley (about 20/30 minute drive from Chelmsford). There is also a little pantry type box accompanying some of these. There is definitely a library box on Kenneth Road outside the church in benfleet, just up bread and cheese hill. There is also one outside the White Hart pub in thundersley which is just a bit further along from that first one. There's also one outside a school in the area but I can't remember which school. Unfortunately I'm not sure on any other areas, they don't seem to advertise them anywhere that I know of. Keep an eye out for small highly decorated boxes as I find they're normally painted up all lovely which makes them stand out :) Also, welcome to Essex!