This paper investigates sound source localisation using an ad-hoc microphone array, where the microphones arbitrarily distributed in a room without knowledge of their locations. The proposed method is applicable to scenarios where microphones positions do not comply with conventional microphone arrays such as a Uniform Linear Array (ULA) and large aperture microphone panels. The proposed method utilizes the amplitude attenuation of the Room Impulse Responses (RIRs) and Time Difference Of Arrivals (TDOA) cues to fit two surfaces across the room and estimate the location of the source. The areas with the least TDOA and the highest direct path impulse amplitude are highlighted as the source areas. Also proposed is an approach to forming subsets of microphones that are chosen such that they can localise the source with the highest accuracy when compared to using all microphones in the room. The approach is investigated for a various numbers of source positions and including additive noise. Results show that the localisation accuracy is increased by utilizing the formed subset of microphones.