Right lets try and sort this out for you.
Firstly are you getting 11.9V with the engine on or off. If your getting it with the engine on then there is something seriously wrong

unless you have the national grid running off the alt.
Second point to note here is that if your using a tomtom charger (like i do) the charger only works when perfectly lined up in the lighter socket. The reason for this is the stupid round end they put on it which makes the center pin move off the contact:frusty: and the fact that they are designed for the new generation of 'power outlets' that don't have the lighter function in them and only offer a power connecetion, and hence are deeper.
The solution is either keep moving it about until it lights up, or go to a boat/(caravan) shop and purchase a bulkhead mounted power outlet socket (they usualy come in a black box with the socket on the side) and connect this into the circuit and mount it somewhere - the socket is twice as deep, and slightly tighter (sometimes too tight but they soon free up)
As for the clock this sounds like it is not getting enough power. - Do you have a digital or analogue on (can't recall years) - i guess an analogue one. Can you rem,ove it, and find out the volatge going to it when the engine is off, on and then with the lights on - sounds as if your loosing power somewhere - if you are -ts time to start tracing wires back, cleaning contacts and silicone greasing them all up - you usualy fine that if it has been waded then left out in the cold and not given a good drying out some of the contacts start getting corroded over time - i just spent 3 days and undid every connector on the beast and used some fine wet and dry to pollish the surfaces up, then diiped each one in a fine covering of silicone grease and then put it all back together after crimping the bullet connectors slightly(the grease semi waterproofs them, but if the contacts are good and tight then does not cause any electrical probs) - All works amazingly now and no more flickering lights for the MOT:biggrin1: