hmm your story sounds familiar, eh robert! i had exactly same trouble - took me loads and loads of goes to even get one right, but when you have nailed that first one they get much much easier.
The only thing i can say is to think about the actual act less and just got for it - i found the more i thought about it when i was doing it the more consistanly bad it was. When i was just able to do it, they just got easier and easier - in fact i actually did better on narrower and technically harder roads than was necessary. now i do them all the time on my street and its barely 2 car widths.
Practice is the key, if you can book yourself a 3 hour lesson with an instructor alone (maybe pay more for it) then i would definately say its money well spent. My irony was i got the u-turns perfected and then missed a 30 speed limit sign on my test about 2 mins later because i was so happy
