Karen
I germinate my tomatoes sitting on top of our outside boiler and bring them indoors once germinated. I use old ice cream tubs, saturate a lower layer of seed compost with Luke warm water, then lay a thin bedding layer dry on top. I place the seedlings on that dry layer, cover them with a thin layer of dry compost, cover the tub in aluminium foil and put it on newspaper atop the boiler. The aim is for moisture to rise warm to drive germination.
I check daily after 3 days and bring indoors as appropriate.
Has worked very well the past three years for around 10 strains of tomato.