A couple of weeks ago, I saw a transporter load of Black Toyota Mirais drive past me in Isleworth.
This morning, again in Isleworth, I spotted this. Another vehicle transporter, being loaded up with another batch of used black Toyota Mirais.

On further investigation, there's a unit in this industrial estate owned by Green Tomato Cars - they're a local minicab firm who do airport pickups - and who have always promoted themselves as a "green" taxi service. Mirais being part of their fleet
I'm assuming these Mirais have all come to the end of their lease and are being gotten rid of. Probably a fair proportion of all the MIrais in the UK I would imagine?!