Anyone who has the luxury of an old 1900s timber floorboards is, in my view a very fortunate Houzzer and would have a very difficult time trying to get anything today that remotely resembled those boards. I have a Queenslander from that era. All Queenslanders has tongue and groove Hoop PIne floors and they were nearly always covered in newspapers with "lino" ( made in England) over the top...so were well preserved. The advice I received about these untouched floorboards that had been seasoned naturally for many years prior to use was to initially "feed them" with a mix of kerosene and pale boiled linseed oil and then stain them if I wanted then give them a couple of sealant coats that would still allow them to breathe. I opted for just a kero and pale boiled linseed oil sprayover whenever they looked "thirsty" and I've used thick rugs to protect them from wear and tear. I've had them like this for 30 yrs or so and am very, very happy with my floors...and they are soft wood. Every couple of years I douse the floors with turpentine as this penetrates the timber and prevents termites, then continue on with the stain, kero and linseed oil mix...then get them buffed. That's just my story that may be or not a little helpful, I was born in Victoria so am familiar with the balck Japan satin that was used down the boards exposed each side of the hall runners....and the boards were the wider ones. Its a pity that multiple sandings compromise the tongue and groove..sometimes such floors need reinforcing from underneath. After acertaining that, maybe a light.soft timber "overfloor"rather than a hardwood would be the go although quite a bit of maintrnance for the first few years. You could stain it any colour you wanted. by getting a light to mid brown or teak stain and give it several coats allowing drying in between until you were satisfied with the colour. Its a good thing to keep in mind that timber flooring from that era was very well and naturally seasoned for years prior to being sold for use...the idea was to seel people timber that would last. I have put on a couple of decks here and am rather disappointed to see that the newer timbers are showing signs of wear and deterioration whilst the original timbers are still as unblemished and solid as the day they were used to build my old home. I think that was a very good lesson for me. All timbers today are kiln dried for expediency so, since they were not permitted to "age gracefully": and gently they are not naturally strong. If ever I do any more timber renos to this place I will be sourcing old timbers form places being demolished. These often cost more...but there's method in that madness! I'd say to anyone wanting their floors to stand the test of time...Buy old timber and treat it as it would have been treated of old. Should have some photos of these floors somewhere. I'll post them if I can

For a cheaper, faster and possibly easier option, take a look at this for some inspiration. The lighter colour of the walls may reflect more light and be a stand out feature of your home. Click on the link and scroll to the image of the polished timber floor with the timber wall and ceiling. Polished timber floors with timber wall paneling

I've used the Feast Watson Liming White. I wanted a finish on pine that wasn't going to look yellow, like the majority of polyurethanes do, but not a heavy whitewash finish. I did 2 coats to get the desired effect, retained the non yellow pine colour and grain showing through. The more coats you apply, the more whitewashed the effect is. Probably a quicker way to achieve your desired affect would be to use a white paint, water based, as a base coat, apply with brush or roller then wipe it off evenly with a rag, then apply a topcoat of water based non yellowing polyurethane to seal. Otherwise numerous coats, 3+, of any of the liming & poly product will be required.

You never mentioned your budget that you're willing to spend. You could add a thicker fill backed insulation blanket - 50mm, 75mm or 100mm are the common thicknesses. Steep roof pitch so would need scaffolding, harnesses, etc.. which adds up quickly. Probably still not enough insulation though but probably cheapest option. Insulation under existing timber linings then reline over the top of that as some have suggested. Working at height though so would need scaffold set up again and working overhead is not fun nor easy. You could replace the roof with a sandwich panel roof. Try Versiclad or Kingspan or comparable. They have a polystyrene type of insulation between an outer metal roof sheet and a metal inner sheet. These are heat laminated together. Again different thickness available from 50mm up to 180mm is common. The 180mm has a R rating of 4.7 which is quite good. Again steep pitch, etc., probably need new ridge capping, etc.. Probably most expensive option...... Keep us all posted on your decision though!