Daly, Gavin. “Napoleon’s Lost Legions: French Prisoners of War in Britain, 1803–1814.” History 89 (July 2004): 361–80.

Also:

http://www.cnrs-scrn.org/northern_mariner/vol06/tnm_6_4_17-27.pdf

And

PRISONERS OF WAR IN BRITAIN, 1756 TO 1815: A RECORD OF THEIR LIVES, THEIR ROMANCE AND THEIR SUFFERINGS

BY FRANCIS ABELL

OXFORD UNIVERSITY PRESS, 1914

During the Seven Years' War the annual average number of
prisoners of war in England was 18,800, although the total of
one year, 1762, was 26,137. This, it must be remembered, was
before the regular War Prison became an institution, so that
the burden was directly upon the people among whom the
prisoners were scattered. Of these, on an average, about
15,700 were in prisons healthy, and 1,200 sick ; 1,850 were on
parole healthy, and 60 sick. The total net cost of these
prisoners was 1,174,906. The total number of prisoners
brought to Britain between the years 1803 and 1814 was
122,440. Of these 10,341 died whilst in captivity, and 17,607
were exchanged or sent home sick or on parole. The cost of
these was 6,800,000.

The greatest number of prisoners at one time in Britain was
about 72,000 in 1814.

The average mortality was between one and three per cent.,
but epidemics (such as that which at Dartmoor during seven
months of 1809 and 1810 caused 422 deaths more than double
the total of nineteen ordinary months and that at Norman
Cross in 1801 from which, it is said, no less than 1,000 prisoners
died) brought up the percentages of particular years very
notably. Thus, during the six years and seven months of
Dartmoor's existence as a war-prison, there were 1,455 deaths,
which, taking the average number of prisoners as 5,600, works
out at about four per cent., but the annual average was not
more than two and a quarter per cent., except in the above-
quoted years. The average mortality on the prison ships was
slightly higher, working out all round at about three per cent.,
but here again epidemics made the percentages of particular
years jump, as at Portsmouth in 1812, when the average of
deaths rose to about four per cent.

Strange to say, the sickness-rate of officers on parole was
higher than that of prisoners in confinement. Taking at
random the year 1810, for example, we find that at one time out
of 45,940 prisoners on the hulks and in prisons, only 320 were
in hospital, while at the same time of 2,710 officers on parole
no less than 165 were on the sick-list. Possibly the greater
prevalence of duels among the latter may account for this.