Hi loonarider,
My first thought reading your post is not to worry about your age. The country is screaming out for more mature workers especially after the Covid pandemic. The Government are on a mission to attract the over 50s back to work - a demographic with life skills not just qualifications or specific experience.
Which leads me onto my next point. Dont just focus on your qualifications or experience to date. Make a list of all your other skills - most of them will be transferable to a variety of jobs. If you arent aware of these ask a good friend to tell you what you are naturally good at e.g. organised, creative, meticulous, people-person etc etc.
It seems obvious to me that you are very motivated by the fact you have chosen to do a science degree in your 40s. Chapeau to you
Let everyone you know that you are looking for a job. It's amazing how much networking can help you find something that isn't advertised.
If you can't find anything suitable instantly have you thought of volunteering. This can be a great way to build confidence and get on the paid work ladder either within the organisation you're volunteering for or somewhere else.
Finally I would treat it like YOU are looking for a job that YOU want and not that you are waiting to be chosen or rejected. Turn the tables and take control.
I think you will be fine. Be confident and positive. Good luck x