Please Help! Engine Misfires And Draining Battery, 3 Garages Cant Tell Me Whats Wrong!

Hi there, my 52 plate 318ci auto, has a few problems which no garage knows how or can be bothered to fix it, ive had many people tell me whats wrong, suggestions have included, head gasket, vanos, ht leads, spark plugs, but nobody can give me a definitive answer.

The car misfires at low revs and revs start edging up from around 800 to around 1500 revs when sitting in idle, when you put your foot on the accelerator it sounds as if the engine is misfiring in the first two cylinders, after a few splutters the engine kicks in and revs fine. Also there seems to be a drain on the battery, ive had the health checked by the rac and they say the battery is in perfect health, but whenever the car has been sitting overnight, in the morning turning the car over is a struggle and sometimes the battery drains flat overnight.

This morning i jump started the car and after straight away the engine was working properly while the battery was connected to another via jump leads, no misfires, no shaking and no splutters, the engine hadnt sounded so good in a long time, took it for a 20 min spin, no splutters at all and i thought miraculously all my trounbles had been fixed, turned the car off, went to restart it an hour later and suddenly all the splutters and misfires came back, but as soon as i connect the battery to another car battery all the misfires went away?

If anyone could shed some light on my issues i would very much appreciate it, the amount of money ive spent on this car trying to get it fixed with absolutly not results is unbelievable. Until today i was under the assumption that it was a vanos problem, but now after hearing the engine run over perfectly while the battery was connected to another has what i think may be wrong with it, but what confuses me is that i know the battery health is fine.