Why can't I keep bay alive?

In 2010 I bought a nice bay pot plant from a garden centre, decent size. I potted it on into a nice big pot in a very sheltered spot on the patio, and in the winter it didn't quite die but lost all its leaves and the following spring/summer limped along for a while with a single stem still green until I gave up on it. In 2011 I bought 2 smaller bay pot plants, which I repotted and left in the polytunnel over winter. And guess what, they didn't quite die but all the leaves are dead and there's just a tiny bit of green stem left on both plants. Now, it isn't local weather conditions because my next door neighbour has a thriving bay in their garden that stands about 12 feet tall and wide, definitely a proper culinary bay. What on earth am I doing wrong?

Bay can be damaged by any temperatures below -5 but it does seem to harden up as it gets more mature.

I have several large bay bushes in my garden - originally from one of the small square pots you can get from garden centres which look like a small shrub, but are usually a pot full of rooted cuttings.  They came through OK with just a few damaged leaves and once separated and potted on, grow very fast.  Maybe try these 

The little shaped ones are softer - probably because they are grown soft before they are shipped to the UK.  We have lost a fair few over winter at work, despite them being under cover. 

I have a lollipop that comes through evryhting just fine, and one in an old plastic pot, ditto

The large one in the ground bought it last winter (2010/11).... no rhyme or reason.

New Shoot knows her stuff so I'd follow her advice if t'were me 

I have exactly the same problem Shokkyy - just can't keep them alive no matter what I do or what the conditions are.