If you want OS 25" maps better to go for the National Library of Scotland collection - they are free online and downloadable.
Northwoods was an odd place -mainly built 1840s we assume by Henry Hawes Fox using his patented concrete floor methods - the Fox and Barrett system. Massive dispute in 1851 on level of restraint. Finally sold to Davey in 1852 who ran it for 25 years. In 1876 taken over by Eager & Seymour who had been the Supt and Steward of St Lukes in London.
The 36 report of the commissioners in Lunacy [1882] says:
In 1875 Northwoods, near Bristol, which had been licensed to Dr Davey, was transferred to Dr. Reginald Eager and Mr T. G. Seymour, the present licensees. The house was then much out of repair, and extensive alterations and improvements were necessary, and, in the main, have been effected; The licensees have, indeed, shown a commendable readiness to accept, and even to anticipate, our various suggestions for further improvement; The reports in the past year upon the condition
and management of this House have been favourable. It is licensed for 25 private patients of either sex, and at the last visit there were on the books the names of 20 males and 21 females. The rates of payment vary considerably; the ordinary charge is three guineas a week, but many patients are received at much lower rates; An adequate staff of attendants is maintained, and we consider that the general treatment of the patients in Northwoods is good. We recently recommended the engagement of a ladies’ companion to assist Mrs Seymour, who now devotes much time to the duties of that office.