To be honest, in EU most things are taxable. Most EU countries will tax you on your lottery winnings, which to me is just weird and unacceptable,but this is how things work here.
This is why accountants are important. They know the system and paperwork and words; they know how you can pay tax in one form cheaper and later instead of expensive and now.
I don't think UK taxes lottery winnings.
though UK lottery winnings will still be taken into account for inheritance tax if the winner dies within 7 years.