Co-sleepers/bedside cots and safety

Today is my day for asking questions, hope you don't mind :-)

We're planning on using what is called in the UK a bedside cot, or in US
speak a co-sleeper - i.e. a cot(UK)/crib(US) with one side missing,
fastened to the adult bed along the missing side, the idea being that
adults and baby have their own sleeping space, but it's easy to get the
baby for feeding and put it back afterwards.

Currently we use a duvet on our own bed. If we were fully cosleeping, I
know the advice would be to swap this for sheets and blankets. I'm in two
minds about whether we really should do this anyway. We could, but I prefer
the duvet, and I suppose I'm not really convinced that a duvet is
significantly more dangerous than the equivalent weight of sheet and
blankets would be. Either way, you have to stop the baby ending up
underneath the covers.

What do any other co-sleeper users do? Any other tips?

TIA,

Sidheag
edd Oct 13th - full term tomorrow!