Looks like standard rockwool to me. Do you have any idea of its age because I'm pretty sure there won't be any asbestos in such things for the past 50 years or so. Even then, it's only dangerous when disturbed and not really a problem if properly sealed within a wall.
But if you're concerned, the only definitive way to be sure is to have it tested.
Just be aware that if it turns out that it does contain asbestos then removal will not (legally) be a DIY job (unlike asbestos in cementitious roofing sheets, for example) and you'll need to use a licenced asbestos removal company.
Lots of asbestos information on the HSE website here: https://www.hse.gov.uk/asbestos/