FWIW, the "BMX" bikes were not; they were Pashly Roadsters, a very old model that is still manufactured in the UK. They were originally designed for cobblestones, and they are heavy and have full fenders. It's quite difficult to do tricks on them.
I felt that the costuming was the most memorable aspect of this film, and I predict that it will win the Costumes Oscar. Sandy Powell has outdone herself this time, especially with the trompe l'oeil costumes in the Royal Doulton scene. The ruffles on these dresses do not
actually exist; they are hand-painted onto flat white cotton fabrics. It's truly groundbreaking artistry.
.
(It is actually likely that Powell will get two nominations; she also costumed the period film "The Favourite" this year.)
Here's an Easter Egg for y'all: the woman who asks directions during the flirting scene between Mortimer & Miranda when Mortimer drops the papers on the sidewalk is someone who SHOULD be very familiar with the houses on Cherry Tree Lane.