Answer my own question. Cruciata laevis aka Crosswort.

and I knew that. its a nice native and is also called bedstraw. I think historically it was used to sleep on too.

Not a plant with which I was familiar and the picture in Phillips book is very poor so I could not id it from that.
Says it is a plant of chalky areas which is odd as it is growing next to a huge Rhododendron (probably ponticum) and the soil here is definitely acidic.

I didn't realise that there was another plant called bedstraw. I grow the Lady's bedstraw Galium verum on the off-chance that a passing Elephant Hawk moth might like to lay eggs, or preferably the Humming-bird Hawk moth!
Mine grows on a poor clay heavy soil, but doesn't seem to mind.

Gosh! I haven't seen this growing wild for years! It used to be a common sight along the lanes here. Yes, long ago people used to use it to stuff mattress ticks (or probably
large sacks). Let's hope it's making a comeback! Just as a wildflower, I mean!

Definitely not Ladies Bedstraw. Try Crosswort instead, Cruciata laevipes. Flowers April to June, but also says on lime!

I was surprised it if was Lady's Bedstraw. I've only seen it growing twice but I'm sure the flowers were white?

I believe there is also a Hedge Bedstraw, which might be the white one? I have a Victorian flower book upstairs, I'll make it my bedtime reading!

Found a few more clumps of it along the lane. So it is in the area.
Should have known it, remember it from my childhood walks with my parents. In those days it was plentiful.
Cannot find any reference to it being a bedstraw though.

its that local/common name thing I knew it as smooth bedstraw as a kid. that's why their scientific names are so important in identification. The laevipes part of its name means smooth.

glad there is more of it growing in the hedgerows.