I beg to differ, the area IS served by Lynx bus. It just takes extra time.
Walking from hotel to Universal takes about 27 minutes. There is also a Lynx bus, but g-maps says it takes 42 minutes to arrive via Lynx bus. OP walks to I-Drive and waits at stop 37 (Park Pormenade Plaza/N Niawassee Rd.) the bus comes approximately every half hour, and stops at Universal. It costs $2.
THOUGH A BETTER option would be to walk over to the New Endless Summer resort (12min walk) and take the hotel's shuttle bus to Universal.
HOWEVER - VIA CAR - it takes only 6 minutes. Taking an Uber would cost $6.55.
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To get to Epcot via bus takes about an hour. OP would walk 21minutes to the Universal Studios bus stop(or take the Endless Summer bus) fomr US bus stop, the Lynx bus takes 34minutes, and drops off just outside Epcot (8minute walk from the IG entrance). VIA CAR/UBER- it takes 23 minutes (traffic allowing). the bus costs $2, while an Uber Uber costs approximately 15.50.
Getting to the other Disney parks via bus takes longer. MK takes about 90 minutes via bus, instead of 22 minutes via Uber/Taxi. (again, non rush hour)
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Sea World isn't bad via bus. It only takes about 39 minutes (though Uber would only take 17minutes). I think again you'd be looking at $2 for the Lynx bus, and $9 for an Uber.
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In my opinion, I could maybe see the walking to US (or taking the Endless Summer shuttle), and maybe take the bus to Sea World. for most of WDW though, I think the time savings of the Uber is well worth the difference in price. If not both ways- at least consider taking an Uber one-way to the parks. Keep in mind, you will be walking the whole time you are in the parks. There's also a significant trade off between transportation time and time in the parks.
If I was constructing a trip budget, I see about keeping food costs as low as possible, then splurge a little more on transportation. I think I'd also skip Sea World, at $100, and spend a non-park day or spend an extra day at Universal. But it depends what kind of combo deal you are offered in the UK. Right now, I see a UK deal on a WDW+ Universal combo ticket good for unlimited entry to all WDW parks +water parks+ US, IoA and Volcano Bay for 677 pounds.