Many people have differing ideas about pruning but most are agreed that the hardest prune should be in springtime, which would be March for most of the UK. I also give my bushes a trim, for tidying up purposes, after they have finished flowering.
I used to be the Head Warden of a Coutry park with a large rose garden and one year the gardens decided to try some different methods of pruning, times etc.... very little made any difference at all....they set St. Patricks Day as the rose pruning day and now used hedge trimmers to prune with!
Cut off the dead flowers, as they finish flowering, at the stem to encourage more flowers and then prune hard as soon as it's a nice warm spring day and you fancy communing with nature a bit. It doesn't matter if you get carried away they're pretty hardy. But by the by, if you've got blackspot on the leaves gather them up when they fall and burn them, it's the one disadvantage of less acid rain...the sulphur stopped the balckspot!
Cut the roses back roughly when they have finished flowering to stop them from getting blown over in the winter then give them a tidy up in the spring .