I am in a similar position to the OP but in the IT field, and I'm just tailoring my CV to start sending it out. I've done a couple of courses to update my skills.
If I fail to get a job through sending in my CV to advertised jobs I plan to:
- contact companies directly and offer my services - on an internship basis if necessary
-contact charities and see if I can volunteer at their head office in something approaching my area of expertise.
At least I will be able to accept a salary as low as I choose. Compulsory service related pay scales are ham-stringing you here.
If you have a child still at school, why don't you ask your child's school if they can help? You may be able to negotiate the possibility of eg shadowing a teacher in your field - and then guess who'd be right there if a supply teacher was needed? Or a private school might be open to you volunteering on this basis.
Or what about retraining in an field where teachers are in short supply? Maths is usually mentioned here. It could be another string to your bow which would put you ahead of the pack.
And to all the smug people saying "Oh well you made your choices, now you have to live with the consequences", well that's very hard when every choice you have made has been purely for the benefit of your children. I know dozens of intelligent, well-qualified women who are mothers of almost adult children, doing unskilled jobs in childcare, Tesco's and John Lewis.
We have a lot more to offer than going on the sick because we can't get jobs.