Finally commute-necessity forced my hand and I ended up with a pair of
Mountain Warehouse Explore long (3/4 length) shorts - mainly because they were cheap (£25) and I could actually look at them / try them on before committing.
After a few wears initial impressions are good - very lightweight and airy polyamide / Nylon with zipped pockets at the sides / arse and two velcro-secured pockets on the legs. Fit is pretty nice with a bit of a taper at the leg and a nice elasticated waist to allow me to pretend I've not gained a couple of inches in recent years.
Both the zipped fly and pockets are a welcome novelty / add security and easy access for important things after the poorly-appointed swimming shorts I've mercillessly subjected to thousands of miles over the past 5+ years (they have held up incredibly well; just are not ideally suited to the task in hand).
Tbh I couldn't ask for much more; especially at the price. Of course time will tell how well they hold up.. if they acquit themselves well there's also a zip-off trouser / shorts combo in the same line that might be a good hedge for when the weather becomes more variable later in the year