Jack,
The " two thingies above and forward of my battery, they look like flasher units to me" are Lucas 6RA relays. Up to 3 are mounted on the face of sill plate between the battery and the wheel well. They are the horn relay, the alternator relay, and (if fitted) an air conditioning relay. If your alternator tests out OK, the alternator relay and/or the Voltage Regulator may be the source of your problem. If your seeing less than 12v across your battery with the engine running, there is certainly something amiss with the charging system. Let us know how the alternator test goes... Just as Joey has described, I have also in the past inserted the 3 warning light bulbs in the wrong sockets in the speedo, but that doesn't account for your battery voltage reading. It is still worth checking the location of the bulbs though, particularly if anyone has been "messing around" in that area. In my case, the high beam light would flash when I was running low on fuel...
-David