That said, whether it's disproportionately common amongst Indian ethnic groups or otherwise, you won't meet that many Patels even in the relevant parts of London. To put things into perspective, the population of Greater London is ~7 million, and there are <100,000 Patels in the entire UK
If you want a better picture of the relative sizes of UK ethnic groups by district (amongst many other demographic factors) then the interactive map at www.censusprofiler.org is awesome.
Schelling, T. (1969). Models of segregation. The American Economic Review, 59(2), 488-493
(Schelling won the Nobel Prize in economics in 2005)
The next generation moves away form these ghettos and assimilates into the rest of London, after a few generations there are only hotspots of the original immigrants left in these places and then usually only if there are strong religous reasons.
If you go into London through the east end (Brick lane etc) the names of pubs are Huguenot (from early 1800s) then there are names of Jewish merchants and tailors on the top floors of buildings (from the early 1900s) then the ground floor is now Bangladeshi.
- by last name: http://www.meertens.knaw.nl/nfb/index.php?taal=eng
- by first name: http://www.meertens.knaw.nl/nvb/english
Most of it is Dutch only, but both have historical data (the one for first names in particular is nice)
Edit - also, it appears that prior to the fifteenth century, the Welsh tended to use a patronymic naming system.
I found it interesting that a couple of zoom levels down, you can see a big cluster of Irish names on the Brent side of the Kilburn High Road, and another in W7.