the valve justs needs replaced,it cots around £15 a set, your land lords a crook as pecavvi says,its his place to do the repairs not yours ,but to replace the valve,remove the top of the tap,(turn main water supply off first)unscrew the tap,(big nut under the handle)this is the valve asmmbly,now buy a new one and replace it same way as you removed it,
mm
February 2013