Posted: 14/07/2012 at 09:53
The leylandii will not grow back-once you have decimated them-but the roots will still there and you are unlikely to get anything into the near-soil-and the soil will be rubbish now anyway.
So you really can't plant any thing in between-unless you go down the container route and place those inbetween- you are then responsible for feeding watering etc
You best bet-but it will cost-is to have the trees removed and the stumps ground out by a professional company-then you can enrich the soil and you might be in with a chance
Others may have ideas for you