Unfortunately, like most things, it's a case of caveat emptor
(let the buyer beware).
As I said in a thread dealing with entirely different facts today, your legal position might be secondary to the moral and PR position if you approach the company with a clear request based on the facts. If you believe you were misled into buying the service based on the calculator and it is not suitable for your needs so you want out of the contract, you have little to lose by writing to the company briefly setting out the facts (your YouTube HD example is a good illustration), asking for release for the contract, agreeing that you will pay any subscription fees due to the point of cancellation and return the device (which is probably locked to EE anyway) if released from the contract.
You can always come back later with a more formal request based on a proper legal analysis of the position, including misrepresentation.
As has been said, 4GEE has a huge 'early adopter' premium. It isn't necessarily that much faster than the most advanced variants of 3G - and once you've got over the '4G' logo, it doesn't really matter whether your connection uses 3G, 4G or what a famous Internet document
termed 'avian carriers
' (i.e. carrier pigeons) if it does what you require.
Mobile networks are not well suited to heavy use, because the capacity is limited and expensive to bolster. The mobile networks have moved away for 'all you can eat' data, with Three policing their 'all you can eat' data tariffs in an attempt to restrict them to untethered phones only, and the other networks going to limited tariffs. When unlimited data was at its height a few years ago, saturation in popular areas was a major problem - the experience was as bad as when you land up in a 2G only area, where the very limited capacity (tens of kbits/s without EDGE) can mean the data service is unusable.
Even UK Broadband, who use 4G technology in the 3.5-3.7GHz range to provide fixed data links in a few locations, use various limiting techniques despite having much more bandwidth than the mobile operators and the advantage of knowing the location of the client devices.