Advice on AL and ML

[SchnitzelvonKrumm12]

Will give as much detail about my situation - whilst trying not to expose myself!
I'm currently (problematically!) pregnant. High risk pregnancy and am suffering from agonising SPD/PGP.
I've been signed off as of 2 weeks ago (for a total of 4 weeks) - my company only offers ssp so it's been a struggle! I'm awaiting physio in a months time although every health professional I've spoken to has little knowledge, or experience in only negative outcomes! Work has asked what I intend to do as they are aware it is a long term condition and in no circumstances can they make adaptations/modifications to my role due to nature of the industry.
I questioned if I was able to use any AL before I began mat leave at, the earliest possible, 29 weeks (I'm currently 22 weeks). She said no as I hadn't accrued any yet due to holiday year starting in September. However, if I don't use AL I'll lose it as we can't carry holiday over. Is this correct? Relatively small company (40 staff) so no HR - just owner and manager's rusty knowledge.
Any advice will be gratefully received!

[flowery]

You will accrue holiday throughout maternity leave, and they need to ensure you are given an opportunity to take it. Taking a chunk before maternity leave starts would seem the sensible way to do that.