No. The tree roots are below your intended bed.

But it will make it difficult for the annual/biennial hard prune or cut back of the Leylandii to take place...

Personally I'd get rid of the hedge before I did anything else. It's a miracle that anything is growing in your garden.

That looks like a big costly job Urbanite. I think it is better if they just make appropriate ajustments for it in their selection of plantings.

Hi Urbanite, that hedge is the best thing in my garden, it acts as a windbreaker, its stopped my shed being broken into and yobs using my backyard as a shortcut

You could put troughs along the hedge bottom next year & plant up with Begonias. That would give you some bright colour along there.

Well if you insist on keeping the hedge (though a good fence and padlock would do the job without sucking the life out of your garden) then pots and troughs are probably the best way to go as you can ring the changes when plants start to fail from lack of light and water (unless you intend to be a slave to the watering can)
A few things will grow (though not necessarily thrive) in the shade under such a hedge - some plants which would probably be thugs in decent soil - ground elder, vinca and golden hop.
Out of interest what do your neighbours think of your hedges - presumably they have to suffer from the shade cast over their gardens, as you don't say that your garden is in the shadow.

I'm just going to have to step in here - Urbanite, if Geraldine wants to have a Leylandii hedge, she's perfectly entitled to without being given a random lecture on what she should have instead. You and I may never plant Leylandii, may hate the blasted things, but if that's what Geraldine has chosen, and with good reason, it's not necessary to be quite so critical of someone's choice - each to his own and all that.

Anyway, provided the hedge is pruned back biennially as a minimum, they do make good hedges. The problem arises if owners don't have them pruned regularly.

Thank you Bamboo - I had only joined this site when I put up this post and was taken aback by the critical comments about my hedge that I didnt come back on until today and when I saw your comment I felt encouraged. As regards the query about my neighbours and what they think of the hedge. Behind the house is a field so they do not block out the sun, and my neighbour and I both planted leylandi at the same time for the purpose of stopping people coming over the fence. As we both have had our sheds broken into and my neighbour had her house broken into also. So they were originially put in as protection

That's okay Geraldine, glad it didn't put you off forever - the trouble with a social site is that, when longer standing members make what might be considered 'critical' comments, they're actually aiming those comments at each other, like a family having a bit of an argument or discussion about the rights and wrongs of something. Therefore, its not really aimed at the poor person who's asked the question - but it sure feels like it is, I'm absolutely certain, it's very disconcerting, and feels unwelcoming. Leaving aside the question of tact or strong opinions being expressed bluntly and possibly repetitively, there is a tendency to forget what the poor new person who's posted a simple question must be feeling - which is why I said what I said. In the ongoing discussion, the principal objective of answering a question properly in a useful manner gets lost, you're not the only one I've seen this happen to - and this may explain, in fact, why people often ask one question and then never return, to some extent.

I hope you found a way to inject some colour at that end of the garden - the container solution was probably the most useful.

Sounds like a very good reason for planting a hedge of them to me.