The majority of homes built after the 1920s have cavity walls. You can get an indication to whether or not your home has a cavity by looking at the brick pattern on the front of your external walls.
Cavity - Likely
If all the bricks are roughly the same size and evenly spaced out, then it is likely that your property has a cavity.
Cavity - Unlikely
If all the bricks are randomly spaced out and are different sizes, it is unlikely that your home has cavity walls.
What if my home is not suitable?
Typically, mineral wool can only be installed in cavity walls with an even width, in properties that are mainly constructed from brick. If you live in a stone house or if your cavity is jagged and uneven, you still may be able to get your wall insulated with spray foam insulation (Technitherm).