Depends what kind of holiday you want.
This summer we're going to an all inclusive resort. We booked a package with Jet2 bus their website. Flights, transfers, hotel, meals, activities all included. Not the cheapest, but really easy. During the booking process you get prompts for various amendments/add-ons - room upgrades, airport parking, insurance, choice of flight times, choice of seat, larger luggage allowance... Of course these all add up so think about what's important to you. In my experience it's usually cheaper to book insurance and airport parking elsewhere.
Last summer we stayed in a city for a few days and then travelled to the nearby coast for a few days. We booked everything separately with the help of Google and a book from the library. So we booked flights with EasyJet, a city centre hotel via booking.com and a beachfront apartment through airbnb. We purchased 3-day travel cards, which we collected from the machine at the airport station when we arrived. We bought our train tickets from city to beach on the day they were needed, having checked that we didn't need to buy them in advance. We ate in restaurants and markets in the city. We mostly cooked simple meals in the beach apartment.
Make sure you order your passport in good time if you haven't already. Apply for a GHIC card. Don't forget travel insurance. If going further afield or off the beaten track then double check the UK Govt's travel advice and whether you need any vaccinations.
Allow plenty of time to arrive at the airport at least 2 hours before the flight. Take sucky sweets in case your ears are affected by the air pressure. It tends to be cool on the plane so I usually wear trainers as opposed to sandals, and take a light cardigan or jumper. For a long flight, take ear plugs and an eye mask.
The last several times I've been abroad I've used very, very little cash. Virtually everywhere takes card payments. It's worth looking at which cards charge the least for use overseas.
https://www.nhs.uk/using-the-nhs/healthcare-abroad/apply-for-a-free-uk-global-health-insurance-card-ghic/
Have a great time!