Changing mat leave end date at short notice

[illStartOnMonday]

I’m due to return to work 4th Jan after 9 months paid maternity leave.

I’ve just found it I may be offered a new job which would be perfect for me and starts on the 4th Jan!

My notice period is 3 months in my current job.

Do I A- just tell work I’m not coming back and risk them telling me I HAVE to work three months notice

Or B- tell them I now want the full one year maternity meaning I will be due back April THEN hand my notice in meaning my three Months notice is during unpaid mat leave.

Can they refuse and make me work?

I know I sound like a horrible employee but trust me they are really bad to work for to the point wile I’ve been on mat leave they’ve lost 8 of a team of 20.

Thank you

If you've had enhanced maternity pay above SMP bare in mind that there might be a minimum period that you need to return to work for or you'll need to pay it back.

It’s ok- SMP only. My employer is tight.
There are no perks with this job