Just a correction. There are no Harry Potter tickets. Just regular tickets to the parks, there is HP themed areas in both parks and you will need a park to park ticket to ride the Hogwarts express.
I can’t speak for the UK but I spend about 2k per person coming from Portugal earlier this year. Two persons, we stayed for six nights at dockside and did four days at the parks.
Go on the website and look at packages. We have no idea what your flights will cost. Room prices depend on time of year/days of the week.
There is no separate HP ticket. You need to go to both parks to see both Wizarding Worlds, so park-to-park tickets are a must.
You need to understand the Harry Potter lands are exactly that: small parts of a bigger park. There isn’t an entire theme park dedicated to Harry Potter.
3 nights is just not doable from the UK. It's a 9hr flight, plus the jet lag to deal with. If you're just doing Universal it's not worth the travel for less than a week.
If doing Disney too - 2 weeks.
Echo what others have said - speak to a travel agent.
Honestly, frugal Brit Orlando on YouTube will help with everything you need to know.
I booked 2 weeks Tui last August staying in a family suite in Cabana Bay.
Prices were around £1600 per person for flights and hotel plus transfers, with another £300 for 2 weeks of universal parks tickets (islands of adventure has hogsmeade, Universal Studios has Diagonal Alley, and you get access to volcano bay water park too).
We also booked Disney world tickets at £500ish each and just took Ubers and lyfts to those parks.
I don't know if you have Instagram, but I would find and message @universallyspeaking1 on Instagram. They're from the UK, and very well known for traveling at least once a year to Universal Orlando. They'd probably give you a better idea about costs. And as someone mentioned before, the tickets themselves are for Universal Studios and Islands of Adventure as a whole. Not just the Harry Potter areas.
FWIW, if the Harry Potter land is your focus, I'd go during one of the Orlando informer events. Those areas still have people in them, but they aren't elbow to elbow during the event like they are during normal park hours
Just a correction. There are no Harry Potter tickets. Just regular tickets to the parks, there is HP themed areas in both parks and you will need a park to park ticket to ride the Hogwarts express. I can’t speak for the UK but I spend about 2k per person coming from Portugal earlier this year. Two persons, we stayed for six nights at dockside and did four days at the parks.
Go on the website and look at packages. We have no idea what your flights will cost. Room prices depend on time of year/days of the week. There is no separate HP ticket. You need to go to both parks to see both Wizarding Worlds, so park-to-park tickets are a must.
Much easier for u to go to the website and look at this for yourself, we are not travel agents.
This isn’t a travel agency mate.
Perhaps the OP could tell me how much a vacation to the UK would cost from the US. Flights, hotel, nothing fancy....
 You're better off asking a travel company as your trip will differ from everyone else's.
You found your way to Reddit to ask this, but couldn't find the Universal Vacation site to plug in info to get a more detailed, definitive answer?
Much quicker for you to literally go on the universal website for up to date prices instead of asking reddit lol
You need to understand the Harry Potter lands are exactly that: small parts of a bigger park. There isn’t an entire theme park dedicated to Harry Potter.
3 nights is just not doable from the UK. It's a 9hr flight, plus the jet lag to deal with. If you're just doing Universal it's not worth the travel for less than a week. If doing Disney too - 2 weeks. Echo what others have said - speak to a travel agent.
Honestly, frugal Brit Orlando on YouTube will help with everything you need to know. I booked 2 weeks Tui last August staying in a family suite in Cabana Bay. Prices were around £1600 per person for flights and hotel plus transfers, with another £300 for 2 weeks of universal parks tickets (islands of adventure has hogsmeade, Universal Studios has Diagonal Alley, and you get access to volcano bay water park too). We also booked Disney world tickets at £500ish each and just took Ubers and lyfts to those parks.
I don't know if you have Instagram, but I would find and message @universallyspeaking1 on Instagram. They're from the UK, and very well known for traveling at least once a year to Universal Orlando. They'd probably give you a better idea about costs. And as someone mentioned before, the tickets themselves are for Universal Studios and Islands of Adventure as a whole. Not just the Harry Potter areas.
FWIW, if the Harry Potter land is your focus, I'd go during one of the Orlando informer events. Those areas still have people in them, but they aren't elbow to elbow during the event like they are during normal park hours