I will chime in with my experiences. I have a BSc (biomedical sciences at an academic university from my home country (not UK)), MSc (medical biology, a 2-year research master from an academic university in my home country (not UK), with one publication (not the main author, though)), and a PhD (chemistry, Cambridge, one publication as the first author). I also have one year research experience in another foreign country (done before starting my PhD) and one year of art school (done straight after my secondary school).
After my PhD I wanted to get into medical communications. I had already done some volunteer/free-lance writing and had been on the committee of two science societies at the University of Cambridge (for which I did photography, web design, graphic design). I didn't yet drive so was limited in where I could find a job (really only IN Cambridge) and this was pre-pandemic so remote working wasn't really a big thing yet.
I think I sent around 30 genuine applications for which I was a STRONG candidate, most were related to medical/science writing as well as some consulting etc as there were so few medical writing opportunities consulting seemed very interesting too as I have strong literature research skills. It took me three months to get 1 (ONE) offer only (I probably had around 4 interviews total). And this was for an entry level job (despite having a PhD: they really prefer you to have a PhD but the money of an entry level job (the only thing they will consider you for) just doesn't compensate for being older and having studied for that long). The job I ended up getting was uugghh, and it didn't work out. I then had another stint of three months looking for work before I got 1 (ONE!) offer for a tech author job. That job was pretty decent, a nice company, but the pay was, again, entry level which with Cambridge rents isn't that much.
There is a fair bit of degree inflation I would say. Both of these jobs described above don't actually require a PhD experience to be able to do them well. But because of how many other applicants there are, there will be some who have a PhD so the employer will prefer to get the most bang for their buck and you basically need a PhD (or perhaps just MSc is ok too) just to keep up even if the experience isn't really needed... It is really crap, but I also unknowingly played along in this game. In my home country you ALWAYS do a Master's if you go to an academic university (before the BaMa system my degree would have just been 5 years, there was no certificate for having made it half-way (Bachelor's), if I understand it correctly). I then continued to do PhD because I love science and liked working in a lab.
I do have to say I didn't look at lab work or Post-doc because I was just really done with academia and working in the lab, after my PhD experience. So I limited myself to relatively rare jobs that are a 'side step' from the career path I set out on when I did Master's and PhD.
This is just to illustrate that it is ROUGH out there. MANY people are 'good enough' for the jobs they choose to apply to. In my home country most degrees aren't really selective to get into as long as you have the right kind of secondary school with at least passing grades, so if you grow up in a system where, if you are bright and work hard, you can get what you want (in education), then it's hard to find out that going to school for even longer is no guarantee for any decent job. Now you not only have to be 'good enough', you have to be the best because for every vacancy you apply to, they usually only look for 1 person. On top of that, in my case, after spending two years on Master's, one year of research abroad, and then four years on PhD, I was 30 when I started looking for a 'real' job, and with that big investment in education and my age, I had certain salary expectations.
And if you are honest to yourself about your qualifications and skills and experience, and you only apply to roles for which you know you are a strong candidate, you will still find that you won't get most roles you applied to. I didn't even get an interview for most of the jobs I applied to despite my strong CV.
It's really rough out there. The only thing I can say is to ensure you only apply when you are a strong candidate. And to keep on applying.
In my case I now have a driving licence and a car. If I had had this when I still lived in Cambridge, I would have been able to apply to many more jobs. So, if you currently don't drive, I would recommend learning this ASAP. Even if you can't afford a car yet. You might be able to borrow a car or lease a care for the first few months if you find a job for which you need access to a vehicle (and then save up to buy a cheap second-hand one).
What is your 'ideal job'? I don't know about chemistry roles specifically as that isn't my field, but I would say a Bachelor's degree isn't really all that much these days. Not in research (neither in academia or industry). You might be aiming too high, although it is promising you got a good number of interviews. For each of my stints of job hunting I kept an Excel file with details of every single application I made. This helped me keep track of my applications so I could chase up on any from which I hadn't heard after two weeks. I also recorded whether I got an interview (or writing assignment, something that is common when looking for writing jobs), and whether I got an offer.
You may have applied to a couple of (slightly) different roles? Do you know whether you were more successful for one than the other(s)? That should help you put your effort towards only the role where you have been most successful so far in your applications, OR if this isn't your ideal job, try to figure out what you are lacking to be competitive for the job that is your ideal role.
I also think that the 'ideal job' doesn't exist, but you'll find that out yourself: no job is going to give you everything you want. And I think that with only an undergraduate degree and so far no offers, you should not expect to find a job even close to 'ideal' as your first or even first few roles, although all of the jobs you will get are a learning experience.
Have you asked and gotten feedback on your applications and interviews? Does your university have a career service/support that you can still make use of?
I hope this helps.