UK thanks to BREXIT put itself in interesting situation where EU standardisation rules does not apply, but nothing else replaced it in many industries.
With PCB design it is very important to understand what you would like to do:
- Draw PCBs to requirements provided by EMC engineer, Electronic Engineer, Compliance Engineer, Mechanical Engineer, System Engineer, Product Manager - this is "Large Corporation Model" in which you are "CAD operator" and it requires minimum knowledge.
- Design electronics in "Small Company Model" and then you need to learn parts of what all engineers above know: product design, which standards apply and why, what tests are legally needed and which customer requires.
Personally I would recommend start reading some tutorials, learn what is used in company you work at read those standards. Maybe there is internal documentation too. Start with simple things, maybe improvements to existing designs to prove you are capable. I doubt you will be given anything "BIG" as first job
All things PCB are covered in the mega standard "IPC-2221"
After 15+ years in industry I would not recommend to use IPC-2221. It tries to solve all problems at once. It does not work. Medical devices are not alarm clocks and different rules apply
You will need to meet EN 61010.
EN 61010-1 is good starting point for laboratory and measurement equipment. However it is rather demanding standard - not sure if you need such strict regulations. Medical are even harder
but commercial are less restrictive. Check what is applicable for products you work with.
Good luck!