You was robbed 'erm. I was talking with an immigrant who paid €8,500 (after deducting grant aid and the €1,200 he got off the scrapyard for his 2015 Prius) for a 251 reg MG5 (same model as yours in a different colour) earlier this year.
Obviously you can't beat diesel for convenience. I doubt many taximen would go EV without grant aid but with grant aid there's no getting away from the fact that you're getting a lot of car for your money where the EV is concerned. However, I don't think that justifies forcing men to scrap perfectly good cars based on age, particularly where some were given age extensions and others weren't. Putting cars into scrapyards in favour of depleting natural resources to manufacture EVs that require twice as much energy to operate and to ship them halfway round the world is never going to be anything other than harmful to the environment. I guess Govt thinking is that if folk see taximen using EVs it may encourage greater general uptake which combined with vastly increasing energy generated from renewables ought to reap substantial environmental gains in the future.