My daughters have both changed their babies on changing stations downstairs, but they use baby wipes, hand washing and/or alcohol gel afterwards. Modern bathrooms don't have very much room for baby mats on the floor, especially when you have twins.
My 3 year old grandsons egged each other on to toilet train, and one highlight was when one of them produced a 'sausage' much to their amusement. After that it became a spectator sport whenever another sausage was produced. Boys!!
Estranged Son and Future Granddaughter
To think that London, or anywhere else for that matter, does not belong to any one demographic