Economical Heating for apartment

Hi all. My husband and I live in a 2 bed apartment in Garrucha. We have no air con, and rely on fans during the summer to keep cool. We are looking for an economical heating solution for the bedrooms and lounge area. We’ve heard gas heaters cause mould, and we currently use a small oil filled radiator for colder days. 

We want to keep our utility bills as low as possible. Has anyone tried flat infrared heating panels? If so, are they any good? 

I already have thermal curtains, fraught excluders, and am buying rugs for the tiled floors. 

I’d welcome any comments. Thanks.