The 'all year round' suit is not easy to find. About 10 years ago, when wetsuit technology wasn't as good, you could get a winter suit and be a bit cold in the winter and a bit hot in the summer. Nowadays if you buy a good winter suit you'll be far too hot in the summer.
My friend just bought a 4/3 Salomon S-Core suit and he went out last week and was baking hot!
I have a 3/2 Rip Curl summer suit and a 2mm long sleaved 'hot skin' - a thick rash vest. This makes my suit into a 5/4 on the top in the winter (although it obviously doesn't perform as well as a proper 5/4. I then have a pair of neoprene Quiksilver shorts (2mm).
This means I can have extra warmth in the winter and if we manage to get some really hot weather and waves or I go abroad I can have what is essentially a long sleeved shorty - just the hot skin and shorts.
I have to say though I just got my new suit, finally laying to rest a 14 year old quicksilver 3/2 and the difference is unbelievable. In November I was still toasty warm without putting the 'hot skin' on.
My main advice is - Never buy a wetsuit without trying it on first. Put the suit on and move your arms through the whole range of paddling motions. Crouch down as close as you can to the floor.
Most modern suits are 'super stretchy' so you shouldn't have any problems. - Watch for looseness around the neck, bagginess under the arms. It should fit pretty much snug all over, but without being restrictive.
Be prepared to spend money on a good suit. The Salomon S-CORE (3/2) is about £170. Rip Curl Ultimate Elasto Slickskin (what I have) is also good (it's the one Bosley wears in Charlie's Angels II). But at the lower end SOLA make good quality suits.
I would also recommend getting one with some colour on the upper half. It will help people keep track of where you are - if you're surfing with your mates, they'll be able to find you again, or if like me you have a wife who is forced to watch - she'll be able to see you easier!!