In those towns, it is seen as 'aspirational' and 'progressive' to give your kids western names because they think it gives them a head start in life.
This is mostly done by the brown/blond and blue contact lens brigade, they have given themselves 'western names' in their workplaces.
The complete irony of course is that these areas like Southall/Hounslow/Slough is that the parents don't even send their kids in their local areas (unless it is a Grammar School or Sikh school). That is because the demographics have changed so much in those areas that people want to send their kids to whiter schools and then they swarm these areas and in turn it into brown schools and they are back to square again.
Well in from North , what usually happens here even the new generation, majority have proper Sikh names, however their nicknames would be more English orientated, such as Harvinder becomes Harvey etc. Anyway I said names don't bother me lol
So why are parents in Southall and Slough (my hometown) doing such things. In those towns it's more like 'spot the white person'.
As for names like Sukhdeep, the Sikhs born here would know the innuendo associated with that name and avoid it. They can go for a simple easy to pronounce name like Preeti. No need for 'Jessica'.
But some people are hell bent on giving their kids a western name and will look for any excuse to so.