I'm a big fan of Sportspursuit, but I suspect for stuff like returns their model doesnt really work, so I'd be wary.
Re wetsuits, I think its worth speaking to someone who knows. My bro bought one and tried it on at home, and thought it was too small as he could hardly get it on. We went to give it a try anyway, and a fitter at the lake showed him how to put it on and suggested he could even get away with a smaller suit!
Fit is all.
But if you want cheap here's some ex hire speedo wetsuits (one hire only it says?!) for £70...
https://shopdesq.imgstg.com/index.cfm?fuseaction=main&OrgID=7529