Vet's been. Dickie has had pen & strep, vitamin injection, steroid injection, energy drench and activated charcoal (twice 'cos I gave him some earlier). Vet's left stuff called "Birp" (truly) in case Dickie bloats.
Vet says that it all comes down to the amount of poison he's eaten relative to his size - so on the plus side, he's eaten about six smallish leaves and he's quite a big, adult sheep. He was also fighting the vet, which is good. He was also burping and seemed to be swallowing better. He was foaming at the mouth earlier - hypersalivation. It's not that they actually salivate any more than usual but the poison stops the gut and the oesophagus closes so they can't swallow. Now he seems to be swallowing.
The next 24 hours are crucial. I've to give him more charcoal before bedtime and again in the morning. If he doesn't eat, he's to have more of the energy drench - it's standard stuff used for twin lamb disease. I'll be picking ivy leaves and breaking out the oatcakes in the morning.
Keep everything crossed for my boy - and thanks for all your good wishes.