We typically use either the Town Quay or the Dan Bran pontoon, both operated by the harbour master. Town Quay is right up in town, so is my preferred option if possible, but Dan Bran is maybe just a 10 min walk down the river.
Town Quay is typically first come, first served I believe, but Dan Bran takes bookings for big sailing rallies, etc., so can sometimes be fully allocated in advance. If you know what day you're planning to go, you can always phone the harbour master in advance and check if there's any major events/block bookings.
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