The aircraft had landed at Southampton and was being taxied to its allocated stand. The No 1 engine had been shut down in accordance with the operator?s SOPs. As it approached the stand, at walking pace, the commander applied the brakes, which had no effect and the aircraft hit signage and the rotating No 2 (right) propeller struck a nearby ground power unit (GPU). During the collision the aircraft sustained damage to the nose fuselage behind the radome, a nose landing gear door and right propeller tips. There were no injuries to the passengers or crew. There were a series of minor factors which coincided to cause this accident. The landing was the last of a day which had consisted of repeated and routine sectors. The absence of the approach checks meant that the aircraft was not configured correctly in preparation for the operator?s SOP in which, after landing, the No 1 engine is shut down and the aircraft taxied to the stand on the No 2 engine. That did not predestine the aircraft to remain in this incorrect configuration. There was a further intervention during the after landing checks with the check of the stby hyd press and ptu cntrl advisory light. However, this check was also overlooked when the crew were distracted by remembering that the aircraft required an OSG check after the last flight of the week which then interrupted the after landing checks. After this, there were no other prompts during the remainder of the taxi by which to indentify the situation. When the accident sequence was underway, and the crew realised what was happening, the co-pilot remembered the stby hyd press and ptu cntrl were off and tried to switch them on, by which time it was too late.