On most Reich taps there is a red/blue plastic marker on the top of the tap lever , prising this off reveals a screw head sometimes philips sometimes allen/torx.
Unscrewing this removes the tap lever and cowl and underneath is a 30mm AF brass nut with a plastic thrust washer underneath , taking the nut off and the washer ( note which way up the washer is) the cartridge will lift out, After frost damage the rubber seal underneath will be displaced causing the leak , reseating it and refitting the nut sometimes fixes it otherwise just get a new cartridge (35mm ) off screwfix note the shape of the rubber seal ,there are two different formats. If the fault persists it can be the two rubber seals on the swivel arm in which case its a new tap . You can get a very similar one off Screwfix but the tails will be different and need adapters to fit them to 12mm pipework on your caravan. done loads of these and have scrap box full of the old ones