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Be very careful with wooden double glazing, it's often badly designed and leads to the double glazed units 'blowing'
Can you not design this out by using plant on muntins / glazing bars like Mumford & Wood sash windows, for example? Granted they don't look exactly the same as a trad sash window but I think most people would be hard pushed to tell the difference.
Prole.-
Although that is the modern way to match the original sash pattern and the glazing bars themselves can't cause a problem with the double glazed unit, the frame still can, and it's the lower part of the window where most of the water that runs down the glass collects which always rots first. There are well known best practices for bedding in and sealing double glazed units in wood, and the trade is improving because it's more popular but lack of a proper maintenance schedule will lead to them rotting and can lead to the double glazed unit being damaged. Then the whole DG (sorry but it gets boring typing double glazed all the time) unit needs to be replaced which involves disturbing all the beading then properly sealing them again. Unlike a normal pane of glass where the putty hardens and drops out, worst case scenario the glass has to come out, normally it's just a repair to the glazing bar, re-putty and paint again.
Having said all this I made a back door for my own place in hardwood with double glazing. I left a 5mm gap around the dg unit using plastic blocks and sealed the beading inside and out with an appropriate sealant. I'll also be able to keep an eye on the paintwork, especially on the beading. It's also easier with doors because access is generally easy.
There are new types of dg unit arriving at normal glass outlets which can be thinner than the old standard 4/6/4 which should allow more direct replacement sashes to be made. However you still have to counterbalance the weight. Having given the subject a lot of thought I am still recommending weatherstripping and insulated curtains to my clients.
Airhead
Sash Windows. I've been paying around £900 for sash windows from the London Sash Window company where I'm replacing sashes in loft extensions. I usually specify wood effect pvc as it looks a bit more natural. The installation is where most companies let themselves down and the guys I use are not that great either, I'm always able to tidy the finish up when they've left but generally these guys just want to get in, rip the old windows out and bosh in the new ones as fast as possible. Most of the materials and methods they use to achieve this finished result at speed are sub par in the medium to long term.
Generally the cost of refurbishing and weatherstripping a sash window is around £900, I've known them to cost more if the entire window needs stripping to the wood, i.e. all the glass removed and replaced with new putty. You may also have to pay a little more if you want the surrounds renovated too. That cost usually includes the inside of the sashes. Quite often sash windows are not in as bad condition as the owner thinks. I usually remove the sashes and replace with ply wood, then the windows are renovated/painted in a workshop, it means no need for scaffolding and access is only required from the interior.
Be very careful with wooden double glazing, it's often badly designed and leads to the double glazed units 'blowing', there are lots of technical reasons for this but the repair market hates wooden double glazed units. I've repaired lots of these units and they are very often a dogs dinner, of course I get to see the worst ones as they are the ones that need repairing! If you do decide to have wooden double glazed sashes, make sure you keep up the maintenance, especially the sealant between the glass and beading, if that seal breaks down or the beading rots the double glazed unit usually blows in short order.
I don't know anyone else that does the job the way I do in other areas, they are bound to exist but like me they probably have a business based on word of mouth or recommendation. I have had clients wait 3 years to have me renovate their windows because they have seen my work locally. Normally I get round to it faster than that!