Hi, it's a Victorian house. I'm having some people out next week to give me a quote but I know it's going to be very expensive! It has to be done though, they're very draughty and I don't want to replace them.
your local county councils conservation officier is the person to contact.
Grants are small. I had some sash windows replaced a couple of years back. Georgian windows costing about 2k a shot. Had about 15k worth of work done to the house and got 5k of a grant. I was lucky, 2 to 3k was the going rate.
I replaced a further 4 window in PVC (Sinful I know) for 2.5k. Measure up the pros and cons before you commiting yourself to working with either the society or council.