Conventional wireless information transfer by modulating the amplitude, phase or frequency leads to an inevitable Rate-Energy (RE) trade-off in the presence of simultaneous Wireless Power Transfer (WPT). In echoing Varshney's seminal concept of jointly transmitting both information and energy, we propose the so-called Generalised Precoded Spatial Modulation (GPSM) aided Integrated Wireless Information and Power Transfer (IWIPT) concept employing a power-split receiver. The principle of GPSM is that a particular subset of Receive Antennas (RA) is activated and the activation pattern itself conveys useful information. Hence, the novelty of our GPSM aided IWIPT concept is that RA pattern-based information transfer is used in addition to the conventional waveform-based information carried by the classic M-ary modulation. Following the Radio Frequency (RF) to Direct Current (DC) power conversion invoked for WPT at the power-split receiver, the non-coherent detector simply compares the remaining received power accumulated by each legitimate RA pattern for the sake of identifying the most likely RA. This operation is then followed by down-conversion and conventional Base Band (BB) M-ary detection. Both our analysis and simulations show that the RA pattern based information transfer represented in the Spatial Domain (SD) exhibits a beneficial immunity to any potential power conversion induced performance degradation and hence improves the overall RE trade-off when additionally the waveform-based information transfer is also taken into account. Moreover, we investigate the impact of realistic imperfect Channel State Information at the Transmitter (CSIT) as well as that of the antenna correlations encountered. Finally, the system's asymptotic performance is characterised in the context of large-scale Multiple Input Multiple Output (MIMO) systems.