I've recently bought a 49UM7400PLB and noticed these invalid service channels, which led me to this thread.
As you appear to have found out, the invalid service channels are 'MHEG' ones which haven't been updated to 'HbbTV' yet, but I noticed that this set does support MHEG in some other countries which haven't switched to HbbTV yet, one of which is Ireland. So I tried a quick experiment, and changed the TV's location (in the General settings menu) from 'United Kingdom' to 'Ireland'. It did some resetting and wiped the channels out, but also changed the 'Programmes' menu to show the 'MHEG' option instead of HbbTV. I did a full retune, which arranged the channels in some fairly random order, but I was able to view '365 Travel' and the racing channel with no problems at all. So that's an ugly work-around, but I don't know if it breaks something else.
Unfortunately, this seems to have disabled all HbbTV channels, but things like BBC's Red Button work like the old teletext service instead of the new graphic version.
Afterwards, I switched the location back to 'United Kingdom', re-input my postcode and retuned again, and got most stuff back with no trouble. I don't use the MHEG stuff myself, but I've got a DMR-PWT655EB freeview play recorder which still supports MHEG in the UK, so I can see them on that if I want.
Hope this helps someone get round LG's premature MHEG withdrawal problem. It would be nice if they just gave us the option to turn it back on in the UK.