Maybe your now berry free spike is from an Arum such as Lords and Ladies.
have you tried germinating a pomegrnate seed? Might succeed in a sheltered garden in London.
I think the Hypericum might be Hypericum "Elstead". H."Hidcote" is usually a poor fruiter.
I grow Bluecrop, Brigita Blue, Blue Jay and Herbert. The first three all crop quite heavily, probably Bluecrop is heaviest. Herbert has less fruit but is the sweetest and best flavoured.
Definitely Birch, probably one of the two native species, Betula pendula or B.pubescens.
Something that is as sudden and drastic as that usually indicates a major problem with the roots. Last winter was very wet, could the roots have been waterlogged?
Some tree genera are better at coping with damage to their trunks and especially the bark, for example Oaks. Magnolias often succumb when their bark is severly damaged.
Could it be one of the annual species of Lavatera?
Top one might be Acer negundo, if you go out and look at the leaves if they are in leaflets rather than a single leaf that would indicate negundo.
I think that no3 is Sarcococca, the Christmas Box, the pictures show leaves rather than the peculiar cladodes found on Ruscus.