Hey TSB!... I feel your pain...
Kitchens are a very hot and greasy environment which can mean that paints won't always work as they are expected to or have done in other/different situations. You are correct in thinking that underfloor heating and AGA's etc. can make using paint tricky.
Tikkurila Feeling/Helmi is a great furniture/kitchen specific paint and will give "perfect" results... as Mark demonstrates in his videos. But, there a few wrinkles that will help; over many years of using Tikkurila on my kitchens, I have found that Feelings/Helmi will drag and close out if the ambient temperature is too high... to counter this you must work quickly and also ease the paint with a little water (5%???), I have also found that it is beneficial to moisten the substrate - Mark prefers is water sprayer - I personally prefer a damp clothe.
What primer have you used prior to using Feelings?
Hope that this helps?