I agree with Mesquite. You'd get a good grounding in it if you get on a course for a day or two. I've dabbled once or twice and it is much harder than it looks.
There's numerous videos on youtube though so spend a bit of time watching those and I'm sure you'd pick up the basics.
I don't know the geology of Essex but you find Flint in nodules in chalk.
As for tools - well you can go modern or stone age. Ie use copper hammers and points or antler hammers and points. I know they can be purchased online but I can't think where just now.
By far the best advice I can give is to wear safety glasses. Flint shards are super sharp, and they would do real damage if you got a piece in your eye. Gloves would be a good idea too.
All the best
Andy