I see that for a wet runway, the take-off distance doesn't have a factor yet the landing does (10%, 1.10) Am I to presume that the same landing factor can be use for take-off as well?
The increase on wet runways for landing accounts for the reduced braking possible. The normal schedules assume reasonable braking is possible. The landing distance factoring for wet grass runways can show a big increase. See the table within the CAA 'Safety Sense Leaflet: Aeroplane Performance' because this gives a factor of + 60% on short wet grass!