My instinct would be to fully cover the BRM with some strong material then attach the plastic grip mesh to that. It would be a disaster if the claws protruded through the mesh and still got caught in the BRM.
I think the featured mesh is stapled to painted timber which could be difficult to grip and may exaggerate the attractiveness of the mesh - if BRM covered the underside of the roof there might be a different distribution pattern of roosting bats.
I must admit I know nothing about LHS bats but as an example of the seemingly impossible spaces bats can get into, when we lived in France, I once found a length of copper pipe stored in my workshop which had something blocking it, when I blew down the pipe to my amazement a tiny bat popped out (good job I didn’t suck) the pipe was 16mm diameter!
We have what I take to be maternity roosts in the small gap between the slates and the felt and I’ve heard bats on the “wrong side“ of the felt in other roofs.
Thanks for the link to the database - for some reason (maybe our incredibly slow internet) I can’t get it to open, it just times out. I’ve used the National biodiversity Atlas several times and there are hardly any records where we are - which doesn’t really surprise me as we’re really tucked away here.