Our house has south facing UPVC double-glazed bay windows in one room upstairs and downstairs. I'm looking for advice for what to do with them. We don't know the age of the windows but maybe 25 years old? The frames are in fair condition, we had a locking mechanism replaced as it had rusted solid (coastal location) and bits are rusty but otherwise okay.   However, airtight they are not. The bubble gaskets on the opening windows no longer seal and I'm replacing those, which m