You could trim the bushes to below the bun pruning or remove say a third a year over the next 3 years .

It isn't that easy to see from your photos but the first may well be a phildelphus and the second could be a magnolia.

Magnolias do not like being pruned!

Somebody has been unkind to that magnolia but as it has lots of flower buds it seems to have recovered. Unless anybody has better advice I would leave well alone this year and perhaps next year thin out some of the twiggy stuff in the middle.
The winter jasmine would probably respond well to having lots of the older stems cut out altogether and it should throw up more from the base.
Taking out a third of the others each year is a good approach to the others. If you remove it all at once you might well end up with another bun.

Thank you both. I think I'll remove a third of the shoots this year then and any obviously dead wood. Any advice as to when to do this would be welcome.

When SHOULD Viburnum bodnantense & Philadelphus be pruned please? As the come into leaf in the spring or after flowering?

I felt VERY sorry for that poor little Magnolia too, Steragram. It seems to have responded quite well though.

Philadelphus should be pruned immediately after flowering.

For Viburnum bodnantense . After flowering, prune established specimens, removing up to one in five of the oldest and weakest branches to the base. Harder pruning will keep the plant compact

The general rule for pruning I use is this:

If it flowers before the end of June, it will do it on wood made last year, so prune immediately after flowering

If it flowers after the end of June, it will do it on new wood made this year, so cut back in early spring

Thank you all!

> If it flowers after the end of June, it will do it on new wood made this year, so cut back in early spring

That wouldn't work for philadelphus which flowers in early June.