It says it has "1 x IP64 rated 1000W heating element " which is rather low powered for an electric heater.
It is certainly very expensive, about £400 more than a common, less stylish electric panel heater with two or three times the power.
If it was me I would get an oil-filled electric radiator, which gives an even heat. It is not as cheap as a plain convector, but nowhere near as expensive as yours.
If you already have two radiators and the room is not warm enough, I guess that it is a large room in an old house, and 1kW is not enough to make much difference. Are the radiators fully hot all over, top, bottom, middle and sides? They should not be scalding, but "too hot to hold for long" like a mug of tea.
But it's your money, and if you have plenty of it, I won't stand in your way.