How did that manage to take so long? I managed to get it all back together this weekend. First job was to install the siren, which I managed to fit by the bulkhead, secured by one of the bolts for the bonnet latch. Finally I completed wiring up the speakers to my head unit I routed new speaker cable to each front footwell speaker, and from there another length to each dashboard speaker. I’ve not bothered to connect up the door speakers as one of them has broken anyway. Each footwell speaker is a Rockford Fosgate Punch, installed by the previous owner. The dashboard speakers are the smallest no-name 40WPC speakers I could find when I bought them about a year ago. I recovered all the old crossover networks when I took the old installation out, but I only re-used the filters for the dashboard speakers.
It now sounds pretty good, to my ears anyway!