Blue Tit, Pink Titbit

Cheeping blue tit nestlings alerted me to the presence of a nest in a gap in the lagging around a steam pipe that used to heat my old propagation house. I found one in the same position a few years ago. The harassed adults were back and forth with juicy green caterpillars, spiders, flies and moths. Then they started bringing something as bright pink as the dog roses in the background. I wish I could identify it.