When it comes to building a house in the UK in a cost-effective manner, there are several materials to consider:

1. Structural Insulated Panels (SIPs): These prefabricated panels consist of an insulating foam core sandwiched between two structural facings, typically oriented strand board (OSB) or cement board. SIPs are energy-efficient, easy to install, and reduce construction time and labor costs.
2. Insulating Concrete Forms (ICFs): ICFs are hollow foam blocks that are stacked and filled with concrete, creating a solid, well-insulated wall system. They offer excellent energy efficiency, durability, and fire resistance, although the materials themselves can be relatively expensive.
3. Timber Frame: Traditional timber frame construction using locally sourced wood can be a cost-effective option, especially if you have access to affordable timber sources. Timber frames are also relatively quick to construct and can be highly energy-efficient when properly insulated.
4. Brick and Block: While not the most cost-effective option, brick and block construction is a popular and durable choice in the UK. Using reclaimed or second-hand bricks can help reduce material costs.
5. Steel Framing: Steel framing is becoming increasingly popular due to its strength, durability, and speed of construction. It can be a cost-effective option, especially for larger projects or in areas with limited access to timber.
6. Prefabricated or Modular Construction: Prefabricated or modular homes, which are built off-site and assembled on location, can help reduce construction time and labor costs, making them a potentially cost-effective choice.

It’s important to note that material costs can vary significantly depending on your location, the size of the project, and other factors. Additionally, you should consider the long-term energy efficiency and maintenance costs when evaluating the overall cost-effectiveness of different materials.