Hi, I've some broken window hinges that need replacing. To simplify the process I'd ideally like to change like for like, so fixing holes are in the same place (measured from the edge on the frame side they are at 36mm, 134mm and 305mm). Windows will be approx 11 years old new at construction. Would someone please be able to identify from photo/s. Thank you. P.S. the glazing units are 40cm x 80cm 4mm glass so by rough calculation the window should weigh around 7kg? does that sound right? so manageable without removing the sealed unit?