Hi, I’m looking to fly to Shanghai from the U.K. for just a 3 day visit to Disney with my daughter.

Unfortunately, you are not eligible for any kind of visa free transit scheme because your itinerary is, as you have correctly noticed, just making a round trip to China without a visit to a third country. You will have to obtain a Chinese tourist (L) visa in advance or to change your flight itinerary. For example, if you would like to think about changing your flight itinerary, you can make your itinerary eligible by introducing Hong Kong. So, your itinerary could look like:

UK - Shanghai - Hong Kong - UK

This itinerary is eligible for 144 hour visa free transit in Shanghai area.