There's not really an official robotics kit that I know of, but there are several 3rd-party options on the market.
If you're looking specifically at Lego, then the sbrick-plus https://www.sbrick.com/ can talk directly to a BBC micro:bit https://github.com/vengit/pxt-sbrick so you can use the micro:bit and Lego together. There are also a huge range of micro:bit accessories from third parties that do robotics, sensing, lights, etc.
It's a pretty comprehensive robotics package, with built-in 4 strong DC motor drivers and 10 servo ports.
It's a project "inspired" by the micro:bit... the original plan was to make it hardware compatible but we were keen to upgrade the mcu to the NRF52 from the NRF51 so this was not possible, so we are working on porting the Makecode environment used by the micro:bit to it.