Straw-like grass ruining my lawn!

Dear All, I have a bit of a problem with my lawn! 4 weeks ago it was looking really green and lush as you can see in the picture. I had mowed it on a high setting as recommended for the first few mows of the season - about 1 notch from top on my Honda IZY which I think is about 6cm. We've had good weather here so I started gradually lowering the height to what I normally cut it in the summer which is 3 notches from lowest on the Honda (about 4cm). And you can see the result! I've posted some close-ups. Basically it's very coarse, brown a bit like straw. I raked some of the bad areas to get this long coarse grass to stand up and then mowed again. Studying the whole lawn it seems that the majority is made up of this coarse grass - there were a lot of seed heads on it earlier in spring all over the lawn.
I suspect this has been a problem slowly developing over the last few years - I've always cut the lawn at about 4-5cm and I'm wondering if this has allowed the coarse grasses to take hold!? Should I start mowing a bit lower to allow the finer grasses to come back? I have Hessayon's lawn book which suggests just that but my lawn undulates a bit and I'm worried about scalping it.
What would you all recommend? Last year I was delighted with my lawn...but this looks terrible!
I have green thumb to feed and weed and I don't have a single weed and no moss which is good at least!
Many thanks, Matt
PS - I can't seem to upload more than one photo so I've just included the close-up!
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MattC76

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On Wednesday, April 30, 2014 3:37:26 PM UTC-4, MattC76 wrote:

You should have mowed it short back then to prevent the undesirable grass/weed from going to seed. And put down pre-emergent crabgrass control, assuming they have that in the UK. It will prevent most anything from germinating and that could work to eliminate it, if it's an annual. But, IDK what exactly it is that you have there. It looks like something that has completed it's lifecycle and is dying. What happens later in summer?
But if it's a grass, it's a real problem. There are very few herbicides that will kill weed type grass without also killing the desireable grass. And the few that are, only work with a very few undesirable grasses and aren't available to homeowners.
I'd try to get someone locally to identify it for you and then you can google for possible solutions.


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