Nigel,
The book cases, whilst not fab or absorbers, help a little in my circumstance - the difference is audible & I did simple tests before & after.

You've some excellent items in stock - and no sign of "acoustic" foam anywhere.
Pity the ditch prevents shipping.

I've spent money, thus far, on some isolation from rooms above with two layers of "decoupled" extra thick Gyprock on the ceiling with a lot of absorption rated Rockwool between them & the original ceiling which also has insulation between it & the floorboards above. Ah, those floorboards look magnificent but even a sock walk sounded like a sock hop.
That cost quite a bit so I'm holding my horses until funds allow me to buy the makings for wall mounted absorbers & some traps.

Cheers
rayc
"What's so funny about peace, love & understanding?" - N.Lowe