UK Phone Numbers ??

I've also seen:

0190 4123456

The area code is 01904.  Moving the 4 so that it appears to be part of the local number instead of the last digit of the area code is bound to cause confusion.  This rearrangement of numbers into strange formats seems to be a relatively recent phenomena.   

By the way, the area codes are not quite so random as you might think from a quick look at a list .  When the original codes were assigned back in the 1950s, the plan was to use two letters plus a single digit (prefixed with a zero, of course).    Taking the the same examples as I used a few posts above:

0PL2  =  0752  Plymouth
0AB4  =  0224  Aberdeen
0BR3  =  0273  Brighton
0DE2  =  0332  Derby
0NO3  =  0603  Norwich

(Note that on British dials the letter O was on the zero, with just MN on the 6.)

The letters were dropped in the 1960s, and codes assigned later were only ever listed with just numbers, but you can still see the original allocations in a very large proportion of area codes. 

So 01904, previously 0904, was originally listed as 0YO4 for York.

London had the earliest automatic exchange network, using the equipment based on the one which Almon B. Strowger of Kansas City designed in 1888. The exchange names were usually chosen for some connection with the area they served (but they also had to be different from any others). MOUntview covered Highgate & Crouch End and the code (called an AFN within the Post Office) was 340 which corresponded to MOU on the dial. Similarly AMBassador (Paddington area) was 262 and FLAxman (Chelsea; John Flaxman was a sculptor and Chelsea was an 'artistic' area) was 352. These codes still work today but the demand for numbers meant that this tidy arrangement ran out of combinations and others with no discernable connection had to be added.
Sometimes the exchange name was changed due to local objections. Bethnal Green was renamed ADVance at quite a late stage in the  planning because the inhabitants objected to being tarred with the Bethnal Green name (the number remaned the same though).  Similarly a block of numbers on LEYtonstone was called KEYstone to pacify upmarket residents who didn't want people to know they had a Leytonstone number)

Hey C-Brit,  Are you another telephone fanatic?    

MOUntview covered Highgate & Crouch End and the code (called an AFN within the Post Office) was 340 which corresponded to MOU on the dial.

MOU was actually 608.  When the Post Office dropped the use of letters in the 1960s, some of the London exchanges retained their existing prefixes (just written as their numerical equivalents) while others were given new ones which bore no resemblance to the original codes.  The MOUntview exchange was given the new prefix 340 at that time.

Bethnal Green was renamed ADVance at quite a late stage in the  planning because the inhabitants objected to being tarred with the Bethnal Green name (the number remaned the same though).  Similarly a block of numbers on LEYtonstone was called KEYstone to pacify upmarket residents who didn't want people to know they had a Leytonstone number)

I wasn't aware of the KEYstone substitution, but there was a similar situation when residents in a certain area who were to be given down-market FULham numbers objected and the name DUKe was substituted (both of which were the same number of course -- 385). 

Another double-name/same-number situation was FREmantle and DREadnought.    The former was the regular name, which served the Olympia area.  Temporary lines installed for the exhibitions used the latter name.

For anyone interested in the name history, I posted a list of the old London exchange names on a Telecom group some time ago:

http://massis.lcs.mit.edu/archives/history/dialing-history

I just work for them, so a certain knowledge of how we arrived at where we are is necessary to get along.