Megane 1.5dci Injector Fault light

[weatebird]

This is my first post on this forum, and it's out of sheer deperation for answers after scouring all the other forums for a solution. I've owned my Megane 1.5dci from new in 2003. Full service history and generally looked after. The story begins when I left the headlights on and flattened the battery (I always thought they swithched themselves off with the ignition, by hey ho). I jump started it with a surge protected power pack and a day later this Check Injector light appears, and it began difficult to start in the mornings with plenty of blue smoke out the back. A mate in the RAC cancelled the fault light and hey presto - the problem vanished, only to return a week later. The car runs fine after it warms up, and power seems the same (slow) as it's always been. Economy is the same as well. Do I go for glow plugs first? Or injector cleaner? It just seems strange to me that by clearing the fault can solve the problem, but there is obviously an underlying fault for it to return. Any ideas?
Thanks,
Weatebird.

[Ray]

i'd go with a glowplug first.

[weatebird]

Right. I've replaced all the glow plugs, cancelled the fault and it ran great - for a month. Light's now back on with same injection fault warning. It failed to start this (cold) morning and ran the battery flat in the process. I'm reluctant to take it to Renault because I have a feeling that they will recommend replacing the injectors which will cost more than the car is worth. Anyone else out there had a similar problem? My sanity is at stake here.....

[davelowe]

Is the battery the original from new?