The Class Rules can be found on the RYA website, somewhere in the "KnowledgeBase/Technical/Class Rules" section.
They can also be found, together with many  other things, on the National Squib Owners Association website, which also has a list of Squibs for sale.

The Squib builders, Parker Sailboats.

Weather
Forecast (from the BBC website).
Isle of Sheppey Sailing Club webcam etc.

Tide
This is not a link, because it would contrave their conditions of use (though you can connect to it and then bookmark it), but tide information is at   http://easytide.com
Note that times are in GMT (though there is a box to click to adjust them by various numbers of hours of daylight saving time).

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