score:11
There is an EU directive about cross-border enforcement of traffic offenses covering speeding tickets (2015/413) but there are a couple of twists:
First it needs to be implemented in national law (like all directives). The deadline for an earlier directive about that was in 2015 and I can vouch that it is now working well between Germany and France and the Netherlands for example. I do not know about Luxembourg but it should be the same.
However, the UK initially decided to opt out of this directive and is a bit of special case. Yet, at the end of 2014, an EUCJ decision changed the legal basis for the directive. This means that it did not find anything wanting in the rules themselves but categorized it as a transportation measure rather than a justice-related measure, thus depriving the UK of its ability to opt out of it.
Consequently, a new directive was adopted that should in principle apply to the UK as well, but with another deadline. Unfortunately, I have not been able to find any definitive information about the exact status of all this. The Parliament is keen on it and I don't think the UK necessarily needs to wait for the deadline but these things take time and I don't think it was already in place last May. Obviously, the Brexit could also have consequences for this down the line.
Finally, note that seeing a flash does not necessarily mean the picture will be usable. I don't have a source at hand but I once read about failure rates above 40% for some speed cameras.
Upvote:4
By the time of this question was answered the answer was: No. See other sources and answer for additional answer.
However be aware that Luxembourg gouvernement keep your plate number and if you get controlled with unpaid fines your car can be block till you pay them (but do not worry they take credit card). Also, severe infraction is transferred manually between countries.