FWIW in 2011 the population of London was 8,173,941
Of these,
3,035,090 identified wholly as English
444,115 identified as "English and British"
94,538 identified as "English and some other identity" (Welsh/Scottish/Northern Irish/Cornish/Irish)
31,952 identified wholly as Welsh
7,081 identified as "Welsh and British"
9,339 identified as "Welsh and some other identity" (English/Scottish/Northern Irish/Cornish/Irish)
53,531 identified wholly as Scottish
11,344 identified as "Scottish and British"
9,339 identified as "Scottish and some other identity" (English/Welsh/Northern Irish/Cornish/Irish)
19,943 identified wholly as Northern Irish
2,530 identified as "Northern Irish and British"
3,238 identified as "Northern Irish and some other identity" (English/Welsh/Scottish/Cornish/Irish)
737 identified wholly as Cornish
141 identified as "Cornish and British"
337 identified as "Cornish and some other identity" (English/Welsh/Scottish/Northern Irish/Irish)
and an additional 2,526,808 considered themselves British but not anything else (so not English/Welsh/Scottish/Northern Irish/Cornish/Irish).