I would recommend contacting a company that has experience working on period properties as windows in period homes were bespoke rather than being made to standard sizes.
The Sash Window Workshop offer a sash window replacement service in London and we have over 20 years experience working on a range of period properties including Victorian terraces. I have included some images of work we have done previous on Victorian homes.
Alternatively, if your windows are in a good condition still we may be able to double glaze the existing windows as part of our unique Bi-Glass system.
We would be happy to provide you with a free, no obligation site survey and quotation for the work if you would like to give us a call on 01344868668 or you can visit our website at: www.sashwindow.com