Nissan Almera Spark & coil Plugs

[woo!]

Does anyone know what could be wrong??

first off every so often it seemed as though it was struggling mostly when going up hills so had it looked at and was told it was misfireing.they changed the spark plugs. car was ok for a bit but then it broke down. had it towed to a garage again they said it was misfiring and that two of the coil packs had blown so they changed those. got the car back and it broke down again. spoke to the mechanic that worked on it and he said the other two would have blown due to the new ones so had the other two replaced. the car still wasn't right so took it to another garage again they said it was misfireing.mechanic ordered some more spark plugs to which i told him they had been changed 3 weeks b4 so he looked further while i was on the phone to him and he found that the spark plugs were wet and that one of the new coil packs had melted. so he advised replace all 4 coil packs and 4 spark plugs and blamed the previous garage for shabby work basicly.but my argument with him was how can 2 lots of spark plugs plus 3 lots of coil packs blow for no reason. . he said i shouldn't have any more problems and that it was running perfect and sent me on my way. i got 2 miles b4 i broke down again. RAC came out had a look and said again that it was misfireing,which by this point i was fed up of hearing, he found that 2 of the new coil packs had melted. i explained to him everything that had gone off so he checked the wires but found nothing. so he changed the 2 melted coils for 2 of the coils i had in the back of the car got it started and followed me to the garage. just b4 i got to the garage the car was starting to struggle again, a sign they were going to go again. The car now is just sat until i can find out what this is.

Please please can someone advise me what it could be?????/