The whole Jurassic Coast is worth checking out, working east from Charmouth, but be very careful and don’t get too close to the cliffs, they’re very unstable and constantly falling. Get some geologists hammers from eBay or Amazon, and do a lot of pebble and rock bashing; the grey shale-like material often shows ammonites inside when you split them.
Last time I was down there I got talking to a bloke who’d spent a fruitless couple of hours looking; I picked up several flat pieces that were by his side and bashed the edges with a pebble, most had ammonites inside! He was practically speechless.
Just had a shufti on the webz and you can get 100gm children’s geologist hammers made by CK Tools for around a tenner on fleabay.