Hi Adrian,
Firstly congratulations on joining our wonderful Forum. We're a rather friendly bunch for what we feel is a serious hobby. You'll never be without help here.
If there's one thing you need to know first before doing anything and that is "you can't kill couch" lawn apart from tipping chemicals on it. Don't be scared of cutting it too low nor putting sand over it still at this time of year as we are just getting into summer and it will be a season that will probably go well into April, so you've got plenty of time up your sleeve.
It maybe good if you could post up a few photos of what you are dealing with so that we can assess it and give you the best advise.
Cheers,
BB.
