Just as a snapshot: using advanced search at Ancestry I found the following numbers of 1911 David Lewis patients for a few selected birthplaces
Lancashire 73
London 37
Cheshire 27
Kent 7
Devon 4
Hampshire 3
Cornwall 1
Dorset 0
Scotland 4
Wales 5
USA 1
For the seven patients with Kent as birthplace I checked where they were in 1901 (just by using Ancestry suggestions)
3 in Kent
1 in Devon
1 in Buckinghamshire (in an epileptic colony)
1 not found in 1911
1 not found at all