In reply to Wainers44:
For real year round use you must be much harder than most. I feel cold in a 3/2 in much less than 30 mins in winter.
Especially with windsurfing etc is not the air temperature, but the water temperature. Dress for immersion even if you don't plan to be in. Comfort and survival time in winter, not making do.
I don't windsurf, but my colleagues do, I prone board Paddle and Surf ski. Prone boards are a wet experience (especially though Surf), skis slightly dryer, both are very active. I will swim in the winter, but prefer not to. Face in water brain freeze is painful and disorientating.
The **general** advice I would give... In the UK your first suit should be a 5/3, gbs with a proper back yoke, or a chest zip . In winter add boots, gloves and hood. (gbs glued and blind stitched - essentially waterproof seams to reduce water flush)
Your second suit should be a long summer 3/2. Gbs.
Your third suit should be a shorty. This could be stitch flatlocked. (mine is long sleeve gbs, and it adds comfort and extends it's usage by a few weeks)
Your fourth suit...
N+1
Adjust to specific circumstances and personal knowledge.
You will be too hot now with a 5/3, but a cheap summer shorty would be ok for quick excursions.
Brands do fit differently, but a good suit using more expensive neoprene will be more flexible and forgiving of different body shapes, and generally have better lining materials (eg Flashdry) than cheaper suits.
I'm using a ripcurl suit that's about 3 years old for winter and spring and my summer suit is O'Neil. Both good, ripcurl better made (IMHO) O'Neil fits me better. My colleagues use a mix of Excel, alder, billabong etc suits. All are pretty happy.