I've just got myself an Ergotron LX Dual Stacking Arm (Part #45-248-026 (polished aluminium/ black accents))with short pole and potentially looking into purchasing an additional third arm (Part #97-940-026) which comes with the required pole collar. Would work perfectly for a triple monitor setup but a little more than the one you've mentioned at c. £216.13 (incl. VAT) for the LX Dual Stacking Arm and c.£99.17 (incl. VAT) for the additional polished aluminium arm.
The above LX model comes with the Notebook tray, which is of little use in your situation but could be sold on to recoup a bit of the cost of the additional arm. Build quality is top notch but obv with prices to match.
I actually use the setup currently to hold up a 20" monitor, 15" laptop with extended screen. I also want a third vesa mounting point to take a tablet mount to hold my iPad off the desk which I use for video calls. I'm hoping to pick up a 38" ultrawide in the next couple months to replace the old monitor at which time the laptop will be positioned above and to the right of the screen with the iPad floating somewhere around the screen (possibly below left). Waiting on a tablet mount and a new desk to arrive before deciding on whether to get the extra arm for the current pole or an MX as below.
The White model (which doesn't comes with the notebook tray) was a little bit more expensive from my research.
Another option would be 3 second hand Ergotron MX models as I've seen those for sale on auction sites for c.£60 - 70 each. or combine one MX with an LX for a little less than an additional arm but with two mounts on the desk (given they are right at the edge of the desk it's much less intrusive than a stand and has given me a load of space back).
Given your 24" monitor size you could also go with the HX arm and Bow but you're looking at like £400+ for that setup.
I had a quick look on OCUK's site and they're listing a 3 way desk mount stand for like £25 for 24" monitors. Doesn't look that funky and has a couple poor reviews but if it's up to holding them up then the price is certainly right if you just wanted a temporary stop gap. I purchased my arm new as could expense it to work but I think you could pick up a pretty decent Ergotron option second hand if you decided what option you wanted and I think you'd get a pretty decent stand for a lot less than new and I think the quality should mean that it will still be in decent nick and continue to work as required.
