I wonder if it's possible for you to offer a non-recorded delivery p&p option.
I suspect you've been burned a lot in the past, but it does make me think twice about buying stuff. It's a pain having to go to the post office, so I tend to wait until there are a few things I want before buying.
I'm not sure what the post office is doing with recorded delivery these days. I came home the other week to find a package waiting at my neighbour's, and the recorded delivery sticker was still attached to the side. I'm not sure if the postie missed it, or if they're ignoring it (I seem to remember reading somewhere that they were going to sign for stuff themselves, rather than take it back to the depot)
Just a thought, but I'd be more likely to give in to the impulse buy if you offered a non-recorded delivery option. On second thoughts...