Steve Fitzgerald wrote:

London never ever had 0207 or 0208 dialling codes. It's some myth put
about by the media every time they have a slow news day and they attempt
to provoke some outrage that Londoners will be confused by these 'new 0203
codes' or somesuch rubbish. London dialling codes went from 01 to 071/081
to 0171/0181 to 020. Nothing more, nothing less.

To be a bit fair the phone code change was not very well advertised in this
form. Rather in 1995 the big message was "it's 1 to remember" aka "phone
codes get an extra 1 added" and in about 2000 the message was more "numbers
beginning 0171 become 0207, 0181 become 0208" than "0171 & 0181 merge back
into a single district of 020 with numbers that used to have the 0171 prefix
now having a 7 added to the start and those with 0181 having an 8 added".

Now I realise the latter is not the easiest message to convey, and splitting
the reorganisation in two would have taken much longer and given everyone
another huge bill to rearrange their hoardings, letterheads etc... but was
any attempt made in the advertising to actually drive home the point that
all of London was becoming a single area? Everything I can recall was a much
simpler "this number becomes that number" or even "the area code changes
again".