You will definitely need GCSEs in English and maths for secondary teaching and English, maths and science for primary: getintoteaching.education.gov.uk/eligibility-for-teacher-training
This has been the case for years and is unlikely to change.
As pp said you could do an adult evening
GCSE course which is likely to be full of people like you (often people who want to go into teaching or nursing!).
You could start the OU course first if that feels less daunting and do the GCSEs later before teacher training.
If you are not completely set on teaching then the HECert might open other options or get you back in the swing of studying, hard to say without knowing what it is.
Have you contacted schools to ask if you can volunteer to get some experience? It might be useful for you and if you can commit to a weekly slot then they may be pleased to have someone reliable.
You say you desperately need to get back into work, are you working at the moment? Teaching will require you to have a degree so at least three years of study (potentially more if you are studying part time or choose a pgce route). So you might need a dual purpose plan, teaching in the long term and something else while you get your qualification.
The 'get into teaching' site that I linked had a helpline and webchat service, if that's useful.
I think your AS Level is unlikely to count towards other qualifications, sadly.