Without any identifying signs or marks, it can be difficult to determine the exact type of concrete blocks used in your house. However, you can try to determine the type by looking at the weight and density of the blocks. Aggregate blocks tend to be heavy and dense, while lightweight blocks such as aircrete are less dense and less heavy. If the blocks are lightweight, aircrete is a likely candidate.
It's also important to note that the type of anchors/fixings you will need will depend on the type of wall and the specific application. It's recommended to consult with a professional or a supplier of anchors/fixings to ensure that you are using the appropriate type for your specific situation.
The age of the block can help to narrow down the potential types of concrete blocks that were used in your house. For example, aggregate blocks were more commonly used in the early '70s, while aircrete blocks started to become more popular in the later '70s and '80s. However, it's important to note that the type of blocks used can vary depending on the location, the builder and the specific construction project.
It might be helpful to take a picture and show it to a local supplier of construction materials or to a professional builder. They might have experience with similar blocks, and could help you identify the type of block and the appropriate anchors/fixings.