I live in Suffolk and am establishing a new bed with old roses (David Austen
mostly). I bought Rosa Wisley (deep pink and very gorgeous) but have found
that when the flowers mature or get wet, the stems are pretty weak and the
flowers droop over so you can't see them. Is there anything I can do to
ensure the stems are more robust eg feed, whatever, or is this a
characteristic of the variety?

I also have had a problem with Rosa 'Arthur Bell' in that many of the flower
heads just seem to flop onto the soil and get muddy etc etc...