The Veterinary Poisons Information Service: the UK's real safety net
UK vets have 24/7 access to the Veterinary Poisons Information Service (VPIS), a specialist telephone service that gives dose-specific, up-to-the-minute toxicology advice for exactly your pet's situation, something no generic online chart can replicate. If you suspect your pet has ingested something dangerous, call your vet immediately (or an emergency vet out of hours) rather than searching for a dose online, they can consult VPIS on your behalf.
Animal PoisonLine and the Blue Cross also offer guidance
Alongside your own vet, UK charities including the Blue Cross and the paid Animal PoisonLine service publish general advice on common household toxins, useful for prevention, but none of them are a substitute for an urgent call to a vet if your pet has already been exposed to something potentially dangerous.