two questions

It won't harm the climbing Hydrangea if you prune out any dead wood. However, let it be a little longer to ensure that the branches really are dead - just keep checking for new growth. Sorry I can't help with the first question as I can't grow Rhododendrons..

What sort of nibbles Steve? Regular round the edge? Irregular? In the middle of the leaf? Do leaves look okay otherwise? If you can post a picture that might help.

Hi Steve Most likely cause of nibbles to Rhododendrons is vine weevil. Actually the grubs come out at night and do the damage not the adult.you may find a hard shiny metallic critter around the base of the plant or try venturing out at night to see the grubs.
V common problem with Rhodos two solutions.
A chemical treatment called Provado made by babybio which claims to only affect the grubs or a totally organic solution is to use
friendly nematodes.
These little fellas only eat grubs and remain in the soil not affecting other friendly visitors or the plant itself.they are mixed in water and sprinkled into the soil at base of plant.your local garden centre should be able to supply both.
I generally remove the affected leaves as they brown off .Oh forgot to ask is rhodo grown in pot or garden? If in pot would repot shaking out as much of old compost as poss.in bin liner.Do not add to your compost area.use the ericaceous compost and the treatment of choice.Good luck hope you save it bonkersbon

thanks bonkersbon, it is the vine weavel and i think i will try the organic option first

spritzhenry ,thanks for the advice , i will give it a couple of months and see what happens

buzzbee, i think bonkersbon is right and will try his suggestions

You re welcome hope to see a pic when back to health should see some progess in 3 -4 weeks so long as it has stopped snowing by then ! think the nematodes might appreciate a bit warmer weather too.sadly weevil grubs can lay dormant so cold weather no problem theyll feed on root system till warm enough to nibble leaves.