Wow CornishFlyer...I wish I was working out of the UK....3 A/C types!!!!!!! In Australia...its 7!!!!!!!!!!!!!!!!!!! ie. Airbus A330 -200 and -300 would be considered 2 aircraft types.
By the way...you've got a very good point in your post.....it could well may be an aircraft config thing. Quite frankly, I personally would rather specialise on one aircraft type and know it like the back of my hand than try to know little bits and bobs about every aircraft type in our fleet.