Which heater for my converted shed/office

[Dracoro]

Just recently completed my new office. 12/8ft shed all insulated (celotex/plasterboard all over), carpeted and electrician sorted the power to it. All good.

Soon, the colder seasons will be with us so need to heat the place as I will work there a few times a week.

So, I need an electric heater of some form. I currently have a 2400W small fan heater but guess this won't be best as no thermostat etc. but useful for heat blasts now and again. What are the pros/cons of what's out there? Convection, oil filled etc.? Should I get a 1.5KW or will a 2KW one be better for that sized office.

Thanks in advance for advice!