Spiffy

- now I won't have to spent a lot of time trying to explain to a sales clerk what it is I'm looking for. (If anyone can tell me the name of the company -preferably in Glasgow, where we live - where you have seen them, that'd be great.) Otherwise, knowing that they exist somewhere doesn't do us a lot of good.

I'm not seeing them on the websites....
It looks like, from the post by JFKimberley that Travis Perkins has them as "hollow dense concrete blocks" but they appear to only sell them as bundles. We just need a few. Am emailing the company, but assume they won't deliver less than a bundle. We are restricted to either delivery or public transportation, as well, so if they don't deliver we need to be able to literally go buy one each, in two separate trips (to be able to get them home).
We need like four of them and two four-foot long boards.