Thank you for your replies.
My friends painter used BIN on her doors. The paint shop said Colortrend all the way and the painter who gave me an estimate, said neither would be suitable. He uses an oil based primer in this situation.
My woodwork is not badly stained, just yellowed.
Previously, in another room, doors with gloss paint were just sanded and then painted with water based satinwood, but the paint has chipped from the side.
That’s interesting about prime 2and BIN being similar. Must check how they compare price wise.