The car is negative earth so you should be getting 12 and a bit volts.

Pretty definitely a dead battery and likely partially short circuited internally so even jump leads might not help.

I'd recommend you go to Halfords and get a Yuasa U1R which fits straight in and works fine - it's what I use.

https://www.halfords.com/motoring/motorcycling/motorcycle-batteries/yuasa-u1r-garden-battery-105605.html?_gl=1*wrbkc5*_up*MQ..*_ga*MTQ5NzQ0MDgzLjE3NTEzNzU5MDY.*_ga_VK44BRER97*czE3NTEzNzU5MDUkbzEkZzAkdDE3NTEzNzYwMzUkajYwJGwwJGgw