If I remember correctly, Foxglove seeds need cool stratification for a month or two to sprout. As for the lettuce, were the seedlings already tall and spindly when they came out of the propagator? Remember also that the human eye adjusts to light levels, so a room that appears bright can still be pretty dark from a plant's point of view.

Foxglove germinate in cool conditions, as Tugbrethil indicates, they don't need heat. I went to a client's garden last week, to discover there were around 40 newly germinated foxglove seedlings in a bed replanted last autumn, and they'd done that all by themselves in the last few months, with the mild winter. I should add they're not there now!

As for the lettuce, it sounds like they got cold - even if your kitchen is warm and bright during the day, at night, its presumably not heated (unless you've got an Aga), so the shock from the warmth of the propagator to the relative cold of the kitchen, particularly a windowsill which can be pretty cool at night, was something they should have been acclimatised to gradually - hardened off, in other words.

Thank you I will learn eventually

If you have some foxglove seed left try sowing it outside. Perhaps another year try it outside in the autumn, which is when it sows itself in the wild.

With your propagator first just turn the heat off. Then remove the lid during the day and put it back at night. then you can leave it off altogether.