What visa are you currently on? You didn't make that clear?
If you are making an initial tier 2 (G) application - if you look at the soc codes and the job descriptions first of all there is no mention of part-time work hours - most jobs are full-time (37 hours/week) that is why they have those associated salary scales with them too.
If you are already in uk on a tier 2 (G) - and wish to work for another company - you need to ensure the company also offers you a cos and hires you for that job for those hours - this is called complementary work - if you had tier 2 (G) this documentation comes when you get the visa. If you are in uk with already a tier 2 (G) - I suggest call ukba to clarify this complementary work to be absolutely informed so you can take an informed decision. Here is a link -
http://www.ukba.homeoffice.gov.uk/visas ... s/#header2
I hope I have understood your question and not just talking nonsense.
Best wishes