Cache lag on NS change for 5 days ??

[Jonathan de Boyne Pollard]

D> The nameservers on micouriers.co.uk were changed to a new hosting
D> service recently (according to nominet.org.uk on July 31st).

It seems, from the description of the consequences, that you forgot 
to perform one of the necessary steps in the process.

<URL:http://homepages.tesco.net./~J.deBoynePollard/FGA/dns-switching-content-servers.html#ChangingOld>

This is _not_ a "cache lag" issue, by the way.  The caches involved
in such cases are still being properly refreshed whenever the TTL 
is exceeded.