Bay windows are brutal for draughts if the seals or frames have aged - we had the same issue and kept patching it until the heating bill basically forced us to replace the whole thing. Funny story: the first "repair guy" we called just slapped extra sealant around the frame and said it'd be fine. Two weeks later, candles on the windowsill were still flickering in a light breeze. That's when we admitted this needed a proper install, not another band-aid fix. We ended up going with a full bay window replacement last winter, and the difference was instant - no more cold spots near the sofa, and condensation basically disappeared. Looked at a few firms and bay windows Uxbridge  had solid options for bay windows specifically, not just generic uPVC replacements. Their team actually measured properly and explained glazing options for heat retention, which mattered a lot for us. Autumn's actually a decent time to get it done before the worst weather hits. Just make sure whoever you choose does a proper site survey, not just a quick quote over the phone.