All that I know about Marley Bros is in this Lock Collector issue 30 article:
It appears Charles Smith and Sons folded into Marley Bros in the 1930’s.
Prison locks in the UK seem to have settled on some standards for appearance and function by the 1850’s, and have largely stuck to those standards, even till today.
They typically use a much larger form factor, roughly the size of an 8×10 sheet of page, than is typical in the US. The locks while having a large form factor, often aren’t very deep ( a little over one inch and often have completely exposed rear sections with no back panel. They are designed for solid (often heavy wooden) doors and the door IS the back panel.
They often have spring activated TRUE deadbolts, that can be activated by a handle, button, or door frame trigger. The bolts shoot through powerfully, often with enough energy to also turn the handle as well. The locks usually have some sort of bolt position indicator, whether by the handle position or clear windows that display the lock’s state.
The locks are often quite handsome with brass handle and escutcheons, and jet black japonned finishes. That is until decades (centuries?) of bad paint jobs take their toll.
The locks by Marley, I would imagine, would fit that format* in some form or fashion.
One company I can’t find anything about is J T Dancer. The blackcountryhistory.org has several of their locks on their website, but frustratingly, nothing about the company itself.
http://blackcountryhistory.org/collections/search/?q="prison+cell+lock"&cb_submit=Search
My Hobbs prison is the only one by that company I’ve seen. There is a lock on display at the Ruthin Prison that I suspect is another Hobbs, but manufacturer name is obscured in the photo. But I believe it would say Hobbs & Co, London.
http://education.gtj.org.uk/en/item1/35240