This isn't exactly accurate. Firstly there are no 8-4 jobs most places though I actually did have one, 9-5, 8-5 most places yes though those aren't the hours you really work. Also, you don't have to be willing to work unsociable hours, it's not a choice, it's your contract and then yes you get the extra pay. I think I was lucky as a very junior doctor in that in most of my jobs my banding meant an extra 50% but this is very variable. I know people that were unbanded for most of foundation so were just on the base. My first F2 job was unbanded so I actually earned less in that post than I had in any of my F1 jobs, that's not uncommon.