1) Will I be offered the speed awareness workshop? Very much doubt it for 38
2) If not then how many points/penalty? 3 pts + £60 fine
3) If I'm offered the workshop then will this constitute a traffic offence and will I need to declare it next time I renew my car insurance? Don't know - i don't think so as i don't think you are convicted if you take a speed awareness course.
4) Silly q but will my insurance premium go up? Possibly, but as long as you have no other convictions, it should be minimal
5) How long will the offence stay on file? Will need to be declared to insurance normally for 5 years, will stay on your licence for 4 years, will be counted towards your 12pts max for 3 years