Tldr: Not much changes. 75% of Britain's space funding goes to, and work comes from, the ESA, which is seperate from the EU. This won't change. The next bigge

Tldr: Not much changes. 75% of Britain's space funding goes to, and work comes from, the ESA, which is seperate from the EU. This won't change. The next biggest chunk is weather satelites, which are also not a part of the EU. The possible change is the Galileo GPS system, which is run by the ESA but owned by the EU. However, given that Britain has been contributing funding for Galileo, I'm guess those involved in the project would like to see the British money continue to come in. There will probably be a seperate agreement covering continued funding from Briain in exchange for continued work on the satellites. (Other, non-EU countries have such a deal)