thank you! And to other posters who added clarifications about this. I can see why the U.K. press are struggling for a direct translation as here allotments are strictly for growing vegetables or flowers only, and a holiday home on one would be unthinkable! But allotment does seem to be the correct term.
Presumably there are clear records of who these spaces are rented to or owned by. I could easily see CB saying (online, or IRL) at some point he’d “buried something at the allotment”, and Police tracking down this parcel of land to him now.
Now we wait to see what that something is, I suppose.