I'm unsure that tagging Delph as a suburb of Oldham makes sense.

I realise Royal Mail classify the Saddleworth villages as part of Oldham for their own logistical reasons, that also cause them to classify these villages as part of Lancashire.

See https://www.openstreetmap.org/changeset/161137917 and https://www.openstreetmap.org/changeset/161137994 for similar discussions.

What do you think?