As title, just bought a SUP and looking for a summer shorty wetsuit for a trip to Cornwall in a few weeks.
IME, on a SUP you will cook in a wetsuit unless you’re surfing and falling in a lot.
A shorty will keep you warm, but like all styles of wetsuits, cheap ones are cheap. They won’t be skintight, if water is able to flush under it then it’s not doing it’s job. They won’t be stretchy enough so will inhibit your movement. Stitched seams will rub. Cheaper neoprenes will rub.
If you need a wetsuit, it’s absolutely worth spending a few quid on one that will do the job. If not I’d suggest one of the thicker rash vests to keep the sun off, and made from a higher proportion of hydrophobic fibres (polypropylene, etc) which keeps them warm as they reduce evaporation once you’re back on the board.
Have a look on wetsuitoutlet.co.uk, any shorties from the big brands will probably be upto the job (o’neil, ripcurl, billabong, excel, etc).