Usually, the larger the radiator the higher the BTU. However, you could also select a radiator that has a second panel or layer. This second layer can significantly increase the amount of heat given whilst maintaining the stylish look of the radiator.
The Radiator Company Ellipsis Single Horizontal radiator, This steel radiator has elegant 25mm x 50mm oval tubes which create powerful lines and pleasing aesthetic. The horizontal is in 3 heights 300mm,480mm and 600mm. The Ellipsis comes complete with a 5 year warranty. Prices from £213.12