Well cleanspade have you found any think we had a chat about this before I can't find 1 out of working stuff this way on ?? Let me know if you have better luck.
There's a fella named Alan he's local , well Kidderminster way he sells them ther, failing that get intouch with Bill net rigger or Andy Kelly contact numbers on here both bang on mate just talk to them they sort ya out
They are 7n blocks for use in block and beam, or below dpc for footings.they can be used any wher but heavy so most wrk above ground level ash blocks 31/2n good solid block and very dense like some on here lol.
Done my young dog last week, ripped a piece of skin off inside of rear leg at top salt water bathe and hydro peroxide to clean out just fit now for 1st season knocked him back for a couple weeks gutted