What an economical 1930s British battleship might look like

What would have been the most economical British battleship design of the 1930s?

An improved Nelson/N3-derived design with modern machinery and 15-inch guns would save design effort while retaining useful combat capability.

Battleships resist cheap design because cutting capability can produce an expensive ship that becomes obsolete sooner. The proposed route reuses an established hull concept, exploits lighter 1930s machinery, and fits nine 15-inch/45 guns with greater length and power. A longer hull and possibly four shafts would turn the design into something close to an evolved F3 rather than a coastal compromise. Reusing design work and building a durable ship offer better value than pursuing a nominally cheap battleship.