Thanks for the reassurances
. To be honest though, if you don't have some changeover arrangement I don't see how you can avoid the possibility of live plug pins appearing somewhere. The generator must have a female socket of some sort on it, otherwise when the generator is running there'd be live pins there. The lead that goes to the house must therefore have a male plug (on the generator end) in order to mate with this. Hence, if the lead is connected to the house while mains is on, you will have live pins on the generator end.
I can't admit to doing this correctly myself though. I have a 'powercon' connector at the house end which has no exposed pins on either the male or female connector, but the generator connection is a 13A plug (since the generator outlet is a 13A socket) so too suffers this issue. In my case however the system is more controlled as I keep the lead locked up somewhere only I have access, so under informed family members can't do anything with it. I realise this is not a practical option for you though.
Going back to the changeover switch arrangement, I guess that a very long extension lead with a 16A plug on one end and a 16A socket on the other is not an acceptable solution (it wouldn't be for me). The trouble is that if you want to do this right, a changeover switch on the incoming supply is really the only option (indeed as I understand it this is the only arrangement permitted by the wiring regulations where the generator is not capable of synchronising to the incoming supply, for which there are pages and pages of requirements to be met). One could perhaps do something with a contactor (big relay) on the incoming supply interlocked with a second where the generator is connected such that both can never be on at once, but this would still require wiring between them.
I assume your current arrangement feeds the house via some pre existing dedicated circuit that supplies the shed. Do you actually use anything in the shed that requires power? If not, one possible solution is to re-purpose the cable going between the consumer unit and shed as the generator supply cable. The end at the consumer unit would be moved to one input of the changeover switch, and the end in the shed would go to a wall mounted male plug.
If that isn't an option, is may be possible to neatly install a new cable between the consumer unit area and shed for this purpose.