Ahhhhhhhh! Bloody decimals... I couldn't see how it could be THAT far wrong... Your box is roughly where I expected it to be and I was looking at old maps yesterday to see if it was marked (current OS 1/25000 maps certainly show VORs).
Incidentally, the three housing estates in the lower half of the box are all former mental hospital sites - there were five more or less adjacent to one another so I think the beacon would most likely be on the golf course site.