There are quite a few clubs listed on agilitynet for east Sussex - but yep I'm afraid that you probably will need to be prepared to travel a bit (and wait a bit) to find and get into a good club. :( ...it is holiday season at the moment too, so lots of people are away and might take a bit of time to get back to you. Give the phone numbers a try - you might get a quicker response.
The Hastings one has a phone number listed as well: 01424-893141
I'm afraid I dont know any other way to find their email address if you couldnt find them on google. Ive noticed there are quite a few clubs that dont keep their details up to date on agilitynet so you often have to hunt around to find contact details.
If I were you, I would read up a bit on agility and agility training etc (and maybe post on here about what to look for in an agility club) so you know what to expect and look for, and then call all the clubs and chat with the owners and visit each of the clubs to make sure you like the way they train etc. This will give you an opportunity to see if you can easily travel to the club as well. Once you have found details of each club, you can put the postcodes of their training location into google maps and check out exactly where they are and how easy it would be for you to get there via bus etc...I guess once you have joined a club you could see if anyone at the club goes anywhere near you that they might be willing to offer you a lift in... or you could get public transport to them and they drive the rest etc?
Another idea would be to look for someone that does private lessons potentially? I know a couple by me that do obedience training and agility training and so they offer private lessons for 'pre-agility' training at your home while you are on the waiting list to join the club for the next beginner course. I would probably only have one of these lessons though just to start you off...they teach you lots of handling & agility basics about teaching the dog to touch a target, spin/turn left and right on verbal command, run along a ladder without touching the bars to teach coordination/rear-end awareness etc.
Or you could do private lessons at a club, as often they will do lessons with you to teach you and your dog all the basics and then by the time you could join the club you would be able to enter a higher class...
If you decide after visiting them that one of the clubs is great but it has a waiting list, then ask them what kinds of things you could do in the mean time - many clubs prefer you not to have any agility training beforehand as different clubs teach in different ways and 'fun agility' is not always done in the same way and can sometimes teach bad habits...hopefully they can give you some ideas to train while waiting.
Some tips that were given to me when we started out was to go back over all your basic obedience with your dog and get them into the 'training' zone and wanting to work with you...do lots of work on having strong recall with distractions and if your dog has never been around a high excitement environment like agility, then perhaps do some training around lots of other dogs to get him used to this? You might find that once you have gone on a waiting list for a club they might be ok with you going along to watch with your dog and doing a little bit of obedience training alongside the agility training - this really gets them used to focussing on you in this kind of environment...I wish I had done this before we started! I learnt the hard way and had to do it while we were training :S
This is a good video of some things you could do while waiting for a club to have a space - they increase rear-end awareness (and are fun!): http://www.youtube.com/watch?v=1-TTFAsGyJ8
Anyway, sorry about the essay! Hope some of that helps :)