Colin, I'm sorry that your question wasn't answered in a timely manner. Pip's behavior is consistent with being intoxicated by a drug, chemical, insecticide, or perhaps bromethalin-containing rodenticide or metaldehyde-containing snail bait. If this isn't possible a complex partial seizure (also called psychomotor seizure) is likely.
Please let me know if you still need help. May I have an update on Pip, please?