Wow, some interesting posts. Thanks everyone.
I tried strips, definitely kept the sparrows out but were also a deterrent to the hens. Now looking to give a plastic owl a regular job....
Just to be clear I referred to the "pests" as infuriating because I have a bird table for wild birds away from the coop where they can (and do) gorge themselves on fat balls, peanuts and seed; lazy as they rob me of layers pellets whilst giving me no economic return for my extra investment; and scavenging (I probably meant scrounging) as they obviously survived before I got the chickens but now see them as a soft touch.
I do worry about disease but it's the economic cost that is more immediate to me. Unfortunately I haven't quite got the time to hand feed them the pellets (I do with their corn treat each evening) so I shall be trying a good few of these suggestions out to find a workable solution.
Thanks again muckahs.