[leslie Wylie]

How hard back can I prune the climber Dublin Bay it has go out of hand

[Good guy]

Renovating overgrown climbing roses
Remove all dead, diseased, dying and weak shoots
Cut some of the old woody branches to the ground, retaining a maximum of six young, vigorous stems that can be secured to supports
Saw away any dead stumps at the base of the plant, where rain can collect and encourage rot
Shorten side shoots on the remaining branches and prune back the tips by one third to one half, to encourage branching
Give pruned plants a boost in the following spring by spreading a granular rose fertiliser over the soil and mulch them with a 5cm (2in) layer of garden compost or well rotted manure

The advice above is from the RHS Website. If you are going to follow it, do it now, before growth really gets going.