The facts of the Bank Stock Office's heating system are difficult to ascertain. Views of the built hall show the central stove and north wall chimney piece as depicted in drawings 47-48. Accounts record the stove-maker A. Ramellie being paid £138:18:0 for 'a heating stove... placed in the cellar' in April 1793, probably corresponding to the firebox and stove illustrated in drawing 46.
What remains unclear is whether or not the full hypocaust system show in drawing 45 was realised. Todd Willmert's in-depth study of Soane's heating systems presumes not, for unexplained reasons. But the appearance of ductwork in drawings 17 and 22 suggests otherwise. Also unknown is what elements of the system would have been designed by Soane and what by expert craftsmen like Ramellie.
In any event, drawings 44-48 illustrate the importance Soane placed on the hall's heating and his willingness to utilise fairly advanced systems, as Willmert has shown. The Bank Stock Office probably remained quite chilly, especially for the clerks and tellers working in winter well away from the central stove. Arthur T. Bolton (The Works of Sir John Soane, 1924, p. 64) reported that eventually independent stoves were placed against the hall's piers.

Literature. T. Willmert. 'Heating methods and their impact on Soane's work: Lincoln's Inn Fields and Dulwich Picture Gallery', Journal of Society of Architectural Historians, 52/1, March 1993, pp. 26-58