I don't know how often it happens but I have heard stories of English clubs offering jobs or buying houses for parents in order to get their children within their catchment area.
ive heard of this too. i also know someone who spent a good 3 months travelling down to portsmouth a couple times a week from wimbledon (south london), before he eventually moved there (as per the "laws"). so yeah, i accept that the laws are subject to quite a bit of flexibility. but nonetheless it does somewhat "help" to stop clubs moving children across the country.
for the most part, the players in our u16 (and younger) setups are london boys. In barcelona, they are genuinely from all over spain. and now it seems from all over the world too, hence their "ban".
one reason i think players should be allowed to move across the country or even between nations however is due to cases like leo messi. under current uefa rules, messi would not have been able to move to barca (not that it seems to stop them anyway). and perhaps without treatment, his dreams of being a footballer wouldve been crushed.