There was a very similar question in today's Telegraph. The advice was:
"Remove all shoots that have flowered. There will probably be new shoots
already growing about 2 feet back from the dead flower heads. Cut back the
old growth only as far as these new shoots.Also, if you can get to the base
of the roses easily, take out some of the oldest and most gnarled stems
completely from gound level. Give each bush a granular rose feed and water
well. Don't cut them hard back all over. If you do, they won't flower next
year"

Jeanne Stockdale

"Judy Donovan" wrote in message
...
Hi,
We inherited a couple of old shrub roses when we moved into our house (I
believe they are Rosa Windrush). They both flower well but unfortunately
they are in a spot that we intend to turn over to vegetables. I'd really
like to keep them and I'm sure we can fit the veg beds around them, but
they
have been supported by an old dilapidated trellis that we need to move now
to start clearing the ground ready for autumn digging. So my questions
a

1. As they're very top heavy they're all the green growth that had
flowers
on is flopping over and I'm worried that the strain will break or damage
the
stems. They're pretty much finished flowering - I know technically it's
not
the right time of year but can I prune them back now to prevent them
getting
damaged?

2. If and when I prune how much can I take off? There's about 3 ft of
old
wood before any flowering shoots start. Is there anything I can do to
encourage new growth lower down the shrub?

Any advice gratefully received!

Many thanks
Judy