With regards to the potential for non IS casualties, Micheal Fallon said on the Marr Show (Sunday) that there had been ZERO civilian casualties as a result of RAF actions thus far in the direct campaign.
I can't comment on that, but it is worth noting that we (RAF) have a habit of coming back with the armaments attached, and are clearly (from the loading footage) using small warheads to achieve the required result when dropped.