Having to go through two sets of lights and then make a turn into sandall beat road and then exit, back on to Leger Way, a junction with extremely bad visibility, and a conflict with bus garage traffic opposite is imho nuts.
For a right turn to be prohibited at the disabled car park entrance then there has to be a sign, there is no sign
The sign on the lampost just before the gap prohibits u-turns from either direction.
There is no mention of right turns being prohibited, and as the central reservation lines are clearly marked as broken then the gap can legally be used for a right turn (or for exit from the car park for a right turn) It is no different in law to the right turn into Sandall Beat Road.
For a clearway (not freeway) to exist then signage has to be displayed like this, large at the start of the restriction and all points leading on to it, and small repeats at a minimum of one mile intervals.

Or for an urban clearway like ths

The road at least further east, starting somewhere just beyond the location of Wickes was once a clearway, but that was a very long time ago, when it was a 60 limit with no traffic lights.
But a clearway does not prevent right turns across traffic, indeed there are two south/westbound right turns on Leger Way that have always existed and did so during the period clearway signage existed on that stretch of road.
But you have my sympathies, after all it is the wazzocks at south yorkshire police you will be dealing with. 