[Sir Trev]

Considering how expensive ovens are you'd not break even on it for many years, if at all. And yes, the fan is only ever in the bottom/main oven from the ones we looked at a few years ago so if you mainly use the smaller top oven you're not going to see much advantage I don't think.

Any chance you can get replacement seals to improve the current one's efficiency? Perhaps adapt your cooking routine to use a far more energy efficient microwave instead?

One last point - a new oven will almost certainly be scrap within ten to 15 years. Same with washing machines and all large white goods these days (some of which are even worse). Our washing machine was an early wedding present and is still fine 25 years later but new ones often last five years if you're lucky.