Im not an expert but it does sound like you have a lot of coarse "weed"
grasses. I find the non-desirable grasses out grow the fine grasses
easily, unless you regularly mow. Usually a mow once a week will keep a
utlity grade lawn in check.
I suggest you investigate what type of grasses you have and what the
general state is, The lawn expert by DG Hessayon is good starter.

Thanks for the info. I've just had a look for The Lawn Expert on Amazon,
and will probably order it.

A.