Free Traffic Legal Advice

Hi I was travelling at 78mph in a temporary 50mph zone of the motorway. It was as so due to road works but was this way for many weeks and there was never a work crew then when I drove through and no changes to road layout etc all cones were on hard shoulder. No one else seemed to go at 50 so neither did I. On the day of the offence I was late for work and travelling at 78 (based on the usual 70mph). I completely admit I am at fault but wondering what will happen when it goes to court what I am likely to receive as penalty (I’ve already bypassed the course or a fixed penalty) any advice appreciated on what to expect whether to plead guilty or look into it more.
Thanks

Edit: I will add the roads were closed at night time for works which is why the signage cones etc were in the hard shoulder. Is it worth me getting any legal advice to plead guilty but go to court and argue for lesser penalty or not worth it? It’s a first offence been driving 10 years never had a ticket before.