I hae answered my own question here, Newhall Court was never a prison of any sort. According to the English Heritage book, The Birmingham Jewellery Quarter, Newhall Court as it now is, was Newhall Works, which was a pin and wire works, with products marketed under the name of D F Tayler & Cp (I used to use Tayler's pins for sewing - they came in a blue tin with flowers on). it was the largest works of its kind in Birmingham, with 400 employees, three steam engines, annealing furnaces, cranes and traversing railways. In 1853 it was producing 6 million pins a day and in 1915 was described as 'the largest pin factor in the world'. Don't know what the 'cells' were for, obviously not cells at all.
Shortie