convection heaters rely on the circulation of air to heat a room; air is blown over a heating element, and then the warm air circulates through the room. They should be used in closed spaces. The main benefit to convection heaters is that they are good at heating an entire room for an extended period of time.
For example this Lloytron 2Kw Convector Heater F2402WH is perfect for the unpredictable weather with 3 Heat settings, 750w/1250w/2000w. A variable thermostat with frost protection. It also benefits from a safety overheat cut-out. it is free standing or wall mountable with Integral carry handles. Dimensions 66.5x48cmx20cm. and its only £25.99.