Today I gritted my teeth and went to the Canon site to get full details of the lens I should have ordered. Only to discover that it was the one that I had sitting on my desk.
I then realised that what I had omitted to do was order the conversion thingy that enables one to attach the additional lens to the camera1.
Anyway, adapter thingy has now been ordered and should arrive in due course.
*Heaves sigh of relief*
1Mine isn't a DSLR, the lens is not removable.)