One of my has gone completely wooden and looks dead, I haven't got round to cutting it but when looking yesterday it is covered in budding leaves ready to open

Yes, amongst the black dried out stems I spotted one or two like that too! In my attempt to tidy up the strangled mess I just did away with them. A neighbour said Clems can go like this but mine have always been fine.

I have never cut back clematis. If one keeps on cutting it back it will never mature. If there is new growth in the spring it will twine around the old stems. It takes several years for the stems to mature and become hard and what looks dead will have buds on it next spring. As far as the aphids, there are natural predators you can purchase should this problem reoccur next year.

Oh I see - thanks. The Deronda's stems have been so spindly for forever now but the Marie B I generally leave alone as strong thick stems. Next time I'll leave and tie in and see what happens.

And Clematis Wilt is very rare. More often than not, when people think their pant has Wilt, it is damage to the stems which cause them to droop. Damage can be from slugs or snails which love to chew off the bark at the base of the stems. When that happens, the plant droops from the top downwards. When it is true Wilt the plant dies from the base upwards.
Have to disagree, slightly with the pruning. Those plants which flower later in the year should always be cut back in early Spring to about a foot high. That way you get plenty of new growth, which is where the flowers are formed.
On early flowers, then yes, leave them alone, only removing dead stems.
There is no substitute for knowing which Pruning group your Clematis belong too.
Daniel Deronda is a Group 2 so it does not need any pruning.
Marie Boisselot is a Group 2 or 3. No pruning, or if you do not want it to be too robust then cut down in February.

I was thinking the very same re the wilt Owdboggy. It's difficult to determine when all the bottom stems are black and fresh stems droopy. Many people say their bottom stems are dried out and spindley looking and breaking off and it's not wilt. Ah well I have hacked off all these damaged scruffy looking stems to about 1ft - no going back now.

I wonder whether to give the Marie Boisselot a boost of Tomatoe feed as there are some fresh green stems with lots of buds growing now. I usually have flowers