For what it’s worth, I think that your grass could be one of the Meadow Grasses (Poa), Bent Grasses (Agrostis), or Hair Grasses (Deschampsia).
All those genera have species that look quite similar to your grass, and all have species that can be found in damp woodland habitat.
But don’t take that as gospel – grasses are a specialist subject in their own right, and my knowledge of them is practically zero. 😳
I have a rust at the moment found on a large robust grass that I thought would be easy to identify – wrong!
I might post the details anyway – just in case we have a grass expert looking in.
Regards,
Mike.