Hi folks,
Thanks for all your comments - sorry I haven't been around (due to a bereavement) to set the record straight sooner.

I mentioned two hollies in my original post. The main one I am concerned about is the Ilex meserveae Blue Princess. This was purchased from a local wholesaler and had its roots wrapped up in a piece of hessian, which he instructed me to plant intact, saying that hollies don't like their roots disturbed and that they would grow through the hessian. I told him that I wouldn't be planting the holly right away, so he wrapped it in another piece of hessian, to keep it from drying out. When it came to planting it a few weeks later, I removed the outer piece of hessian, but planted it with the original hessian still intact. Some new roots had already started to appear through the cloth even in this short time, but I don't think they got damaged in the planting process as they were only starting to peep through. The holly is about four feet high - I don't know how old it would be, but I would imagine that it's fairly young (it's not one of those expensive mature samples you can buy). There are about half a dozen vertical branches with not many side branches. It has lost most of its lower leaves to about halfway up each branch. It is planted in front of a three foot (fairly solid) fence in a raised bed facing south west, so it gets plenty of sun. There is a good depth of loamy topsoil on top of a clay base and would be fairly well draining because of the raised nature of the bed, but we did have an awful lot of rain this summer here in Northern Ireland! The bed is covered with the weed membrane and a layer of bark chips.

What I would really like to know is, even if the hessian is the problem and I remove it, will the holly grow new leaves where it has lost them or will I end up with a leggy specimen?

The other holly I mentioned is an Ilex aquifolium J. C. van Tol, which probably has more berries than leaves! It came from the same source but was pot grown (no hessian involved this time - sorry for any confusion in the first post). It has one main leading branch about four feet tall with a few short horizontal branches. It was planted in the lawn, south westerly aspect and four foot fence behind it. Although it has not lost leaves to the extent that the Blue Princess has done, it still looks very spindly and has not done anything all summer in terms of new growth, although the berries are very nice!