wishbone, carpet with thick underlay is an option but will not solve the problem entirely, I have to disagree with Mommah's concrete solution, an old house doesn't need that level of invasive work to reduce cold air from a suspended timber floor. Serotoninisd - I don't know of a product that can be installed like that, unless you lifted a small area of the floor to crawl into and found you had 4ft space to work in below, otherwise its just not practical.
the space below the timbers must retain ventilation so moisture can dissipate and does not lead to damp/mould/rot, that's why the majority of these homes were and are still build with vents at that level - (you'll often see old perforated bricks or metal grills near the footpath level on suspended timber floor buildings - and these should not be blocked)
best to deal with the drafts and cold as two separate things - one requires insulation the other an air membrane/barrier.
1. lift floor boards, removing skirting if necessary (you may wish to number the underside of boards for relay)
2. check space underneath, ensure vents remain open, check if there is any damp/required timber replacement
3. lay hemp cloth or similar material between joists (or chicken wire or geo-textile)
4. install insulation preferably sheeps wool or hemp but mineral wool (rockwool or equil will be fine)
5. install Vapour check (same thing as an Air-tightness membrane and tape/seal with correct product to the wall perimeter
6. reinstall floor/skirting
best of luck with it.