Passport:
You will need a valid UK Passport with at least 6 months left on it.
Proof of stay:
Paul W will have this as the hotel bookings are in his name.
Travel insurance:
You will need European travel insurnance for the duration of the trip.
Global health insurance card:
This replaced the old E111 card.
The GHIC card is available from the NHS website and is free of charge.
https://www.nhs.uk/using-the-nhs/healthcare-abroad/apply-for-a-free-uk-global-health-insurance-card-ghic/
Poof of funds:
You may be asked to provide proof of funds for the duration of your stay. This could be in the form of a bank statement or, mobile phone banking app or show cash.
They have concluded that visitors to the EU would need on average 45 euros per day.
(this check is very rare)