[Isonstine]

I did too! It felt ultra modern at the time..

Manchester tried something similar with their BBC radio station. That didn't work either, in any of their incarnations.  

(Source: Logopedia)

That's not really a fair comparison. GMR (Greater Manchester Radio) existed in the same era as GLR (Greater London Radio) and both are initialisms based on a logical name to describe the area they serve.

LDN was a stylised contraction of London and was an aimed at unifying different media channels under a single brand. It could have all been different as one plan was to name the newly created London TV regional news programme as 'London Live' which was already in use on radio and online.