I'm fairly new to Mumsnet, but I have to say I have learnt so much from the Good Housekeeping threads. Definitely my favorite section 
So, flattery over, I'm hoping you can help with a windows query (can you feel the excitement building?)
Our house has double glazing, but fairly old I think and not PVC. It's an Edwardian house so the windows are quite large. In a couple of them there is condensation in between the two panes of glass iyswim. DH thinks this means the windows need replacing, but MIL reckons they need taking out, cleaning and resealing only. What do you think? Or is there another solution? I'm very good at ventilating, not drying washing inside etc 
And if they did need replacing, is it £££ to get non PVC windows that sort of look like sash windows (what we have atm - we moved in in September)?