Expensive Boys Toy or ROI sense check

I love a gadget and before I go and blow £11Kish on a PW3 and Solar ...that I REALLY want....But I need a sense check

I live alone in a 3 bed victorian terraced with an EV, average 4500Kw per year on 'intel Oct go' bills around £800per year ... I claim more back my Company for use of the EV. Gas is about £600per year ... i can fit a max of 10 panels

I'm thinking I'd be better off throwing the £11K into paying off my mortgage.

What do you guys think? Am I caught up in the 100's of solar adverts on my web use and thinking OMG a new toy to play with or will I get a decent ROI in 8 years?

EDIT; Thank you everyone it's been really informative. My plan now is to scale my toys and get an Givenergy battery set up and max out on solar input. I can access interest free funding, so I'll take a chunk off my mortgage and get the Solar and Givenergy