Hi there, I also have laurels (about six) at the bottom of my garden and we let ours grow to about 30ft (they are 35 years old) and then decided to lop them. It took my hubby and I a year to finish this job as we could only get rid of one branch per week in our weekly green rubbish colln.Well we completed the job and cut them down to about five foot each and it did them the world of good, like yours they were brown/yellow and looking poorly. Dont forget too that we have had the driest year on record so they must be suffering. I would prune yours down as much as you can and then you will find that this will do it good. A few weeks ago we did this to another of ours and it looks green and lush now with the new growth. They are pretty tough shrubs.

thanks,much appreciated