Yes, I think O3 is likely the Portland, UK company. Probably closed for Corona
Is the suit loose with your weightbelt and weight-vest on and hood up? Do you get cold? If not, maybe it's good enough for now?
I have the impression that Omer wetsuits are quite slim fitting, suited to adolescents and Italians perhaps? You should check their size charts. I think Beuchat are more normal fitting for many older adult British men. I got a Mares camo suit on sale for about £120-£130 which just about fits my stocky frame in theory but actually fits surprisingly well in actuality. The 5.5mm neoprene is quite stretchy, so quite accomodating for different shapes and sizes. But stretch means the neoprene is thinner than 5.5mm when you put it on. But it's fine, more warm enough for me even in March - although I don't feel the cold as much as some. It was made in Cambodia.
I expect most brands are now made in SE Asia, so much of a muchness perhaps. I like the look if Polo sub semi-camo designs and they are made in Rome. I like the Omersub Camos. I like the Beuchat wetsuit designs, mainly black, the quality looks better than average and they have some novel innovations. There was an antipodean company that produced what looked like it might be the best/fanciest wetsuit. Rob Allen wetsuits might be a good, robust option for "manly men". I wouldn't touch Picasso stuff with a barge pole, some of their sizes are/were way off, perhaps sized for Asian market. Bad/odd size issues with Seacsub wetsuit too, despite carefully checking their model-specific chart.
The Turkish Apnea brand wetsuits from spearfishingstore.co.uk might be worth a look, if on sale. The guy in the store insisted my son was a small so, against my better judgement, he tried to get into a small but it was way too tight and we didn't have time to try the next size up.
They were charging camo prices for plain black wetsuits at the time but, in their recent 30% off on-line sales, probably a much better deal available now/soon. The quality looked good enough. The owner is trying to sell the business now though and is not currently selling in the shop, just on-line.
Refer to model-specific size charts, these tend to be more accurate but they don't tell the whole story e.g. cuff sizes and thigh width/length.
A made to measure suit e.g. by eliossub, polosub or the cheaper Greek company some use now is worth considering.