What was the name of the house where the conspirators made their last stand?

The house where the Gunpowder Plot conspirators made their last stand was Holbeche House.

After the plot failed in London on 5 November 1605, Robert Catesby and several surviving conspirators fled into the Midlands. They raided Warwick Castle for supplies and gathered weapons before reaching Holbeche House, a mansion owned by Stephen Lyttelton, late on 7 November.

The fugitives tried to dry damp gunpowder by a fire, but a stray spark ignited it. Catesby, Ambrose Rookwood, John Grant and another man were badly burned, while Grant was blinded. The next day, a force led by Richard Walsh, Sheriff of Worcestershire, surrounded the house. In the ensuing exchange of gunfire, John and Christopher Wright, Catesby and Thomas Percy were killed; other plotters were captured.

Holbeche House is sometimes spelled Holbeach or Holbeache. It was not the site of the planned attack: the conspirators intended to destroy the House of Lords in London and then trigger a Catholic rising.