Morning lads, @psDevUK and @Abhijit,
This is the issue with using “!important” in your CSS files. I’ve learned to only use it as a “hotfix” as it overrides stuff down the line.
I’ve been wanting to redo the themes myself, but due to the testing demands and etc I haven’t gotten to it.
If you want to do it with theme, I’d recommend going with a class on the relevant elements and then targeting said class with CSS and utilizing the “!important”. Make sure to put it on the end of your theme, in order to overwrite anything else that’s being specified for the element.
If you have any issues, hit me up with some code and i’ll be happy to help 
Until then: happy hunting!