I've added jump roping 2-3x times a week to my weight lifting routine and find that it has helped a lot with paddling for some reason. 

If you can find a rowing machine, that also helps. There's a ski machine at my gym and I'll try to do 1 min with both arms and 1 min with alternating arms (something that Nathan Florence recommends) with 5-10 reps depending how tired I get.

But besides that, it sounds like you're on the right track!

I 2nd the hyperfreak in terms of comfort. We don't experience as cold of weather in Southern California but I find that the chest zip is a bit easier to put on as opposed to the zipless. I don't find it as much of an issue with allowing water coming in but I assume the zip would be better in the cold. 

As for recycling, Ripcurl usually takes in old wetsuits. I don't know what their policy is in the UK but I assume it's the same worldwide.