If you booked your flight and accommodation together from one company, you are covered twice over, by two different pieces of law, for two different losses.
Against the airline, under EU261 or UK261. The operating carrier owes the fixed compensation for a three hour delay or a cancellation, exactly as it would on a flight-only booking. Being part of a package changes nothing about this.
Against the tour operator, under package travel law. In the UK that is the Package Travel and Linked Travel Arrangements Regulations 2018, with equivalents across the EU. The organiser is responsible for the holiday being what they sold you. Losing a day of a seven day trip is a real loss of value, and that is a separate claim from the flight compensation.
Most passengers only ever make one of these, usually because the operator answers as though the two are the same thing. They are not.
Keep them in separate emails. Combining them is the surest way to get one reply that answers neither.
Operators frequently reply that the delay was outside their control, or offer a goodwill voucher against a future booking. Neither of those disposes of the EU261 claim, which is a legal entitlement owed by the airline and can only be settled in vouchers if you agree in writing.
If the delay was caused by a technical fault, a crew shortage or the aircraft arriving late, the compensation is owed regardless of what the holiday side of the business says.
Flight-inclusive packages sold in the UK are ATOL protected, which covers you getting home and getting your money back if the company fails. That protection is one of the genuine advantages of booking a package rather than assembling the trip yourself.
Check the flight side of your claim