Are you actually sure that would be the more ecological option?

I can answer that one - it absolutely wouldn't. An electric car is vastly better than a new ICE car from eco perspective, if you're buying new. But keeping your old car and driving it instead will always be more ecologically sound.

Oh I know. Just wanted to give wffurr an opportunity to find out for themselves :)

16 years is a good run. You're well past the point of diminishing returns on repair costs and the poor mileage from that vintage is adding up.