UKC

So as a more hefty or rotund member of the climbing family clothing has always been a bit of an issue as the mainstream brands don't cater for people with a waistline over 34 inch.

For last few years I've used a pair of oversized wranger jeans to allow for flexibility, durability etc but never been happy in them as felt I was climbing in pair of clown trousers.

Recently bought a pair of Dickies Glyndon pants and love them for bouldering. 

Firstly they go up to 42 inch so cater for us larger gents. 100% cotton so very, very lightweight but with nylon ripstop pockets (rear and cargo) and a drawstring as well as belt so a good fit. And ankle elastic closure if you want to have the clinched look.

Finally a pair of trousers that look like they belong on the wall (same styling as Moon/Prana) but made for us heavier blokes.

Downside you'll struggle to find them for less than £80 but a one off investment I feel.

Totally personal option 

Important for those gents that drink: do they show up piss splashes ?

Personally as long as i'm comfortable I don't care if something looks like it belongs anywhere, I wear what I want when I want.

I wear sports shorts for climbing.  I'm at the wall to climb, not to look good.

Ronhills - you'll look great

Yep.  And the likes of Moon stop well short of 'hefty' or 'rotund', they basically have no interest in producing a pair of trousers you can get your arse in if you're anything other than a stick insect.

Personally I don't give a hoot about dressing in clothes that look as if they belong on the wall, but the Simond stretchy jeans available from Decathlon are very good indeed.
https://www.decathlon.co.uk/p/men-s-stretch-climbing-jeans-vertika-blue/_/R...

Alpkit Kraft. £55, jean-ish canvas but with a nice stretch. I first bought a pair of XXL and they were too big (I'm a 36 or 38 depending on the season, XL was much better). Available in S/M/L leg with the latest version.

https://www.marksandspencer.com/big-and-tall-cotton-rich-stretch-chinos/p/c...

They should do you.

Lidl builders trackie bottoms £8, fit even the fattest of climbers. 

I hear they look particularly good on cracks?

I tend to find there is no builders bum cleavage on show whilst I am crack climbing in these bottoms.

As another ‘robustly built’ gentleman, I’d undoubtedly look like a condom punched full of lard in a pair of Ronhills.

I’ve got a couple of pair of stretchy decathlon walking trousers ( https://www.decathlon.co.uk/p/men-s-nh500-regular-off-road-hiking-trousers/... )that I use for most active stuff. They fit well around the legs without garrotting my beer-baby at the waist, but I’d go up a size from normal, as per Decathlon standard. 

I thought this was going to be an advice page on where to buy trousers that have secret drinking compartments... Jeans with hipflask pockets or built in de-hydration pouches, for sneaky, go-anywhere drinking.