MG TF 1.8 135 2004 OBD P0313 Misfire with Low Fuel error

My baby is an MG TF 2004 1.8 135 with 35k on the clock and an excellent service history.

She has developed a misfire over a number of weeks culminating in a EML flashing and staying on. The misfire is there when engine is cold but it gets much worse as the engine heats up.



There is no coolant loss or coffee coloured foam under the oil filler. The fuel filter was replaced in Sep 2013; spark plugs replaced Sep 2012; cam-belt kit fitted 2010.



Three months or so ago I had a problem with the alternator and broke down with a dead battery. I was towed by the AA to a nearby auto-electrician who said he had "replaced the spindle" and charged me €200 for the privilege, even though I'd only asked him to diagnose and let me know the cost to fix... setting aside the rip-off, could a botched/poor alternator fix be the cause of the current problem?



Possibly related, although purchased new in 2012, I had to trickle-charge the battery once due to it losing all charge overnight in the cold weather a month ago.



The local garage couldn't get their OBD kit to talk to the MG's ECU. I bought a OBD tester off Fleabay for £20 and found a P0313 Misfire with low fuel error. With such a generic error, I'm thinking that I'll have to start replacing the cheapest electricals first such as the HT leads and coil packs?



What would be the likely cause of the error and the best approach to diagnosing/solving the problem?



Sorry about all my questions :)



Regards...

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