my lawn has been taken over!

It looks nice and will probably need less watering than grass in the hot weather.

"wild lawns" are very in now.

It looks a bit like one of those geranium type plants.

Yes, I'm pretty sure it's one of the hardy geraniums.

Could be a hardy geranium. There is one very small one with pink flowers. It acts like ground cover if you let it and will quickly spread. Or there is a slightly bigger purple flowered one. If you want to get rid of it there will be lots of rhizomes to pull up. But it is pretty as it is. (Unless it is something else altogether)!

Thanks all. Yes, I think it is a hardy geranium, and it seems intent on colonising every space going in my garden! Personally I rather like it - my lawn looked like a bit of a wildflower meadow last summer. I think mainly I feel gulty because all the other houses in my 'row' have grass lawns! - though that may not be true once all this is over...

Are they daisies?

My lawn and flower borders gets completely swamped with 'babies tears' - not sure what the real name is.
I pull it out regularly but can't seem to eradicate it completely.

Looks like buttercups to me. Wait until they flower, then you'll know.

You also have dandelions (which insects love) and at least one lesser celandine in there and, no doubt, various mosses — a natural wild meadow. People actually make efforts to achieve such! Leave it all to flower. It'll look lovely, especially to wildlife.

I wage constant war on buttercups in my lawn, but...you do have to admire the rotters don’t you!

Why wage war on them? They're gorgeous if you just let them flower.

You might even find you have more than one kind: meadow and creeping and, possibly, even bulbous.

Looks like buttercups to me.

It looks like creeping buttercup to me, which is very invasive.

I'm trying to achieve a wild meadow, well more of a strip, Baggs but some plants just take over, eg creeping buttercup, dandelions.
Convolvulus has lovely flowers but I don't want it strangling everything else.

Creeping buttercups and dandelions are classic flowers of wildflower meadows, callis.

The exotic-looking pictures of so-called wildflower meadows we see associated with packets of mixed seed are usually not of native plants that would normally have been found in ancient UK meadows. Most people don't realise this, unfortunately.

And the fact that non-native seeds are included means that these flower mixes are not as useful to native insects as, one hopes, people who sow them expect.

Plantlife.org and BSBI (the Botanical Society of Britain and Ireland) have lots of info.

native wild flower mix

Well this says native so unless the BHS are lying why not try these.

Of course native species are quite specific to different areas and soils. Plants that thrive on, for example chalk uplands, who not do well in wetter, darker soils.

This is part of one of my wildflower areas. The yellow flowers are Cat's-ear which flower later than dandelions. Check out the clover too. There are also rushes and sedges in there and various mosses.

As well, of course, as some Northern Marsh Orchids, one of which is pictured.

Deffo creeping buttercup. I made a decision to leave my lawn to nature this year, create a natural meadow. However I'm now getting nervous . I'm afraid the nettles will be 6ft high.
Has anyone tried?

Nice one Baggs! We are invaded by violets.

It looks like a geranium (cranesbill) to me, clearly self seeded so you must know the mother plant. I would take a guess at endressi which is a peachy pink, flowers from April/May until late autumn.
Personally I always feel it is better to go with nature. That part of your garden doesn't want to be lawn so don't force the issue.
As the geranium likes it there you can encourage it by removing the dandelions, lamium, and anything else growing amongst it then splitting the geraniums and planting evenly all over. It will root quickly if you water it and by summer you will have a sea of pink flowers which is excellent at suppressing weeds.
Wildflower meadow is another option but Labour intensive to be kept pretty. For large parts of the year is will simply look abandoned and neglected.

@Grammaretto I turned a wide strip in front of my house into a quasi wildflower meadows a number of years ago. It was quite a project. I used seed and plugs. Neighbours would donate things like buttercups they wanted rid of and any seed packet remains. Anything that looked the part went in. I wasn't precious about it being genuine wild flowers believing that as long as the bees were happy it was fine with me.
It got better and better until last year when some rampant ugly grass took over. I now don't feel I have the energy to fight the grass as it is so difficult to dig out and I'm not up to it.
Am now contemplating covering it all in black plastic for a few years then having it dug over and planted with groundcover, or perhaps decorative stone chips. So sad. It was lovely.