Two groups of employees came from different sites and joined up as one team performing the same job on a new site. One group is on 'Tupe' (salaried) and the other group are paid an hourly rate. The two wage structures remain unchanged however the salaried group are in effect making 47p more per hour than the hourly paid group. The different pay structures have been in effect for 9 months. All are outsourced permanent staff contracted to the same company.

Should we not all be on the same pay structure?

Why does the language sound more like homework and less like something you are experiencing - and essay homework at that.

Even if it isn't homework this is a question for the employers and not some random internet site.
You need to understand what TUPE actually means in reference to employees rights in relation to existing terms and conditions of employment

Those salaried accepted those terms at the time of hire without regard to what other employees make. Those hourly did the same.

Nobody forced either side to accept the job or associated pay / benefits.