Starting problem with VAUXHALL ASTRA

[Christa53]

Hi can anyone help????
i have a similar starting issue with an 05 reg astra hatchback. with 67k on the clock and fully serviced. when trying to start car in temperatures below 15c the car starts but then drops revs and dies, it is erratic in idle when I finally get it started especially at junctions when it again cuts out on me and I have to restart it. it is like a jerking horse until it settles down and drives normally. sometimes when starting in conditions like this the power steering locks and it is hard to steer but again when the car settles down there is no problem and drives okay. my mechanic has checked it for any faults and even took it to the vauxhall garage to be put on their computer and no fault codes have been found. it has had a new battery, throttle body checked and cleaned just in case. had anyone any ideas on what is wrong? I have never had this issue with any car I have owned and it is literally driving me up the wall. ps the car is fine in warm/hot weather maybe I should move abroad

any help would be much appreciated