New Doors and Windows
Can we draw your attention to Accoya? This is a sustainable softwood that has been specially treated by a firm called Accsys Technologies to make it rot-proof. The makers guarantee it for 50 years, though TRADA (the Timber Research And Development Association) which is a long-standing and well-regarded not-for-profit industry body says it should last 70 years.
It has been around for quite a while now and has become distributed to everywhere, and has a track record of use in the building industry. The industry is very conservative and doesn't use anything that has not been used before, so that makes the introduction of new materials slow.
Accoya is better than the best hardwoods for longevity, and is slightly more expensive than them, but on the cost of a manufactured product that is immaterial. It is good for all external uses, such as decking and cladding, but is particularly useful for doors and windows.
Note that uPVC windows are not usually reckoned to last more than about 20 years, and in any case do not look right in conservation areas.
If you need new external joinery, check it out. Try Google. Talk to joinery firms, here are a few websites.