How to change career as a software engineer in UK at 30 s' age? I am BSc graduate(Mathematics, Physics and Chemistry) I have no any software developing experience. But I love to enter the field. Currently working as production planner in manufacturing and going to migrate UK.
You will want some sort of training - even self training. If you aren't a programmer already you will need to become one in some popular language. There are online courses and other face to face instruction that you might be able to find locally. It can be hard to learn from some online programs since there is less of a "goad" provided by a professor who grades your work and gives feedback. 

There are a lot of self taught programmers, of course. Many of them are deficient in key areas required for actual development. Even such things as data structures and algorithms might be missing. Don't fall into the trap that all you need is some familiarity with, for example, Java or C. Go a bit deeper. 

The UK has an excellent "distance" program in CS run by Open University. You can use them or other 'local' UK universities to give you what you need. 

You might also be able to connect up with some open source project, initially as just an observer and later, as you learn some things, as a contributor. You can do this sort of thing from anywhere that has internet connectivity. But better if you can find some assistance. Even another person or two with similar interests so you have someone to discuss issues with. 

Your background will make some parts of your learning regimen easier, I think. 

Learn a lot and write some interesting programs. Large ones if possible. And don't neglect the human/organizational side of software development. Modern programs are built by teams for the most part.