The other place for kitesurfing in Sussex which is less frequented by both kitesurfers and the general public is the beach at Brighton off Madeira Drive just between the banjo pier and the marina wall.
This site has the advantage of not having any beach hazards up to 150 meters before the marina wall where there is another pier.
Otherwise it has no groynes for a large stretch, with the exception of the naked, old wrinkly variety on the nudest beach which can be hazardous to your mental health!
Madeira Drive (Brighton, Sussex)
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You should set up so that you will not have to kite to close to the marina wall or the new construction, giving them a 150 meter birth to be safe as steep walls can produce nasty updrafts, which will prove dangerous and drag you into the wall if you get too close. The shore break here is generally very harsh so you should only come here if you have experience of dealing with this and as other kiters are rare then you would be better off with a kite buddy. All this said there are some great wave conditions to be had here on a strong south westerly. This would be my choice of the two.