It appears to be XZ209 the example in use with JARTS at Boscombe for just such training scenario’s

See the picture on Demobbed, from when they were based at St Athan: http://http://www.demobbed.org.uk/image_view.php?a=24605&s=xz209.jpg

Many thanks Mark. Went through the latest copy of W&R but couldn’t find one that matched.