Hello Jon P. I am an enthusiastic collector too, although I'm not
completely clued up on it all, I will try to help.
1. The daffs and tulips with solid heads are Britains. I believe they
were the earlier versions.
2. The blue flower heads you received with your rockery agin are
Britains and I believe were randomly packed along with White and
Yellow.
3. Hyacinths, Lupins, Delphiniums all had 'solid' and 'detachable'
versions. Though I don't know which were the earlier.
There, that's about all I can tell you. I may be wrong, so please do
not quote me.
As to you needing a dealer, I have the two items you require. I have
a cap stone for a pillar and 4 gate brackets. I am not a dealer but I
do have a few spares.
Hope the minimal info I have sent you is of some help.
Best Wishes and keep collecting, Tracey.