It's good of you to reply. I have stripped all the cut branches of their leaves (we had to cut the hawthorn back) to dry separately. I found that the spindly new branches are indeed full of thorns but the thicker sections of branch don't have the spikes too close together and so I have either snapped off the couple of thorns that are there or cut a section between them. I'm going to make sure there is nothing at all protruding from the those sections I put in their run. I looked at PiggieParcels where they now have apple twigs (I bought from there too!) and have gone for similar lengths and sizes. So it should be ok. I'll be very careful about what I give them, though. I'm guessing that twigs/branches will take a long time to dry?