I had the 'engine check light' come on so i took it to nissan and got the codes, 
P0345 Camshaft poition sensor 
P0011 and P0021 Bank 1 and 2 variable valve controllers, which were at -17 degrees, should be between +5 or -5 
They checked the timing chain tensioner protrusion which was at 14.5mm, they're techs 'think' the chain could be stretched which is causing the other problems. 
Then the next day i had problems starting it after work, as if the battery was nearly flat. 
They quoted £1000 in parts then labour on top to change the chain. The car has only done 43k miles. 
Any ideas?