I think this is one of those debates that's often characterized as an
either/or thing, when it really needn't be.

I grew up in Romford, another town that's been swallowed by greater
London. As anyone who's ever been to Romford will know, it's not
exactly devoid of Essex identity, and I suspect that most residents
would claim they live in Essex. (This includes the local MP who for no
reason other than a hatred of Ken Livingstone, as far as I can tell,
wants the London Borough of Havering to cede from the GLA).

However, it also shares features elements of cultural identity with
East London generally in a way that, say, Basildon doesn't. Moreover,
in a practical sense, thigs like transport are better planned from City
Hall than from Chelmsford, as more people will want to travel around
the conurbation than out into Essex.

I don't see any contradiction there. Romford is a suburb of London in
Essex, in the same way that Bexley is a suburb of London in Kent, and
Wood Green is a suburb of London in Middlesex.

Jonn