In reply to siwithington:
I think you need to test ride some bikes .
If you believe carbon fork will equal better handling and comfort over rough roads well its not that straight forward.
In my limited experience these are my thoughts.
Carbon fork with canti brakes can give dangerous brake judder, mainly an issues on cyclocross bikes. Cured by fitting v-brake. Fact Carbon forks do flex noticeably (all forks do to some extent).
Carbon fork is less harsh than alloy fork? maybee
Carbon fork is equal in comfort to steel fork but lighter? maybee
If comfort is a concern then this could be achieved on any bike through Tire Width/Pressure, Handle Bar Width/Spring and Bar Tape.
It may be better to plump for better wheels / group set than Carbon Fork?
I recommend you take 40mins out and watch this YouTube video on bicycle economics.
I cant emphasize enough, Test Ride.
You may have your heart set on a bike to then have it dashed by it just not feeling right when test ridden.
Good Luck