Maternity leave extension

I think it depends on your workplace honestly, I used my holidays that accrued while I was off to extend mine

Maternity leave is 52 weeks max. However, you can request annual leave or parental leave (usually unpaid).

Mat leave is 52 weeks max but you can take a “career break” if offered by your employer, most likely unpaid. Info here https://www.gov.uk/career-breaks

I would speak to your HR department if possible. They should be able to tell you if you're able to take extended leave or a career break or similar