!989 heaters are still pretty good, Margaret. The advantage of newer models is no magic cure. They mostly have better control facilities so they can be fine tuned to your needs.
Energy in = heat out ................ whatever the heating medium may be. I wouldn't take too much notice of the ads. They still consume energy in exchange for providing heat........... and if they're on full-price instead of off-peak, then you'll be worse off .......... warmer during the day, but worse off financially.
Electric systems can often give surprisingly good (low) cost-to-run figures......... but, only with a very high level of insulation. Important for all systems, obviously, but especially for electric.
Spend your money on draught-proofing (if it's an older flat). Maybe even floor insulation (if on ground floor), or loft insulation if you're at the top of the building.
If it's a brand new flat (with today's high insulation standards), then good quality thermal curtains/blinds make a great difference.