Hey Kazza,
If it makes you feel any better, I'm a daily lunch time gym junkie, and have been since I hurt my back 3 years ago - but I am still sore from Saturday as well... it's a good thing, not a bad thing.
If you're already stepping up weights, then you're getting stronger.
I can highly recommend reverse push-ups for Windsurfing strength training, as it's not primarily the biceps holding the rig, it's your upper back/lats.
I've found a youtube clip that is the best example I can quickly find. But basically a strap with handles or a bar, or a boom tied to something higher like the roof, or a tree, which allows you to lay on the ground and pull yourself up with your hands slightly wider than should width apart...a push-up in reverse. This will work out "windsurfing parts" of your muscles.
I did watch this with the sound muted, I can't vouch for his advice :-).