If it's not too far, tell them to check out Ramsay Road allotments, very near The Wernley Pub on the Wolverhampton Road.
There are more plots not used here than actually are! I keep reading about waiting lists whilst shaking my head!
I had to argue a lot to a lady at Sandwell council to get my plot as I was told they were all taken, but talking to plot holders down there, it was obvious they hadn't been used for years.
Even now they bill me for the wrong plot number!
Sandwell council have not managed this zone well, so a lot is overgrown, and will need some work. And they may tell you that they are occupied, but the fact is most are not actually used, which is a shame.
There are about 12 folk who do tend thier patches well, and it is a battle against weeds from the other unkept plots!
At the time I got mine, Warley Road plots were also in a bad way, but I've not been up there since.
I'd suggest trying to get a key and investigatiing plots yourself!
Good luck.