Once again, many thanks for all the answers. To comment on a couple of points -
I'm not so much thinking "Hmmm, Engine bay = good place to store tools" as just thinking that it's a useful general storage space and I noticed this when having a good look over my friend's boat. I'm aware that when cruising you only have what's on the boat with you and you can't just "nip out to the garden shed to pick up the ....." so every cubic centimetre of storage space has to earn its keep. The engine bay seemed to be dry and secure so was a useful area to store some items. It wouldn't be the place to store your best crockery, but it seemed like a useful place for anything that doesn't have to be instantly to hand but should be reasonably accessible. I had wondered how storage space on a cruiser compared.
I also get that you can add roof boxes for additional storage but there is a height limit depending on bridges and tunnels. The engine bay just "exists" and doesn't require any additions or modifications. Again, I get that exactly how accessible, dry, clean, etc., it is will depend on the individual boat.
Arthur makes a great point abut "getting the boat that talks to you". I've looked at some ads for boats that on the face of it tick all my boxes but looking through the photos and specs I just think "No. I don't like it". Equally, I can see an ad for something that shouldn't work for me but does. I'm absolutely open minded about stern type but my gut feel is that I'd prefer a trad