192 comes from BT, which no longer has a monopoly on Directory Inquiries; the others come from rival companies -- and they're cheaper. 11 88 88 comes from an Irish company called Conduit; 181 181 from a company called The Number.
192 is the old number for directory enquiries and is being phased out. All the new services start with 118.
Somewhat inexplicably, BT chose the unmemorable 118 500 as their new number.
The other two mentioned have both got memorable numbers (as well as almost saturation advertising) and so could be in a position to erode BT's usage.
Just a word of warning on this, most of the new ones make the money this way. With BT you make the call and they give you the number you write it down or whatever and then you ring it up. With the new ones they say do you want the number or do you want me to connect you if you say yes then the call is carried on their lines and costs 45p+ a minute.