Bonesie, just as a last check. Have a look at the earth connections. Clean them up and try starting again. I had similar a few years back on my 4/4. Battery in the rear near the axle. I used a long booster cable direct from the battery negative to the starter mounting bolt. Car started ok. Morgan used short earth leads, one from the battery to the chassis nearby, used the chassis to link to another short earth cable to the starter mount. Bypassing these showed a poor earth somewhere. New cables and clean connections was all that was needed. Battery was ok. I did eventually change it though as I spotted a small crack in the casing near one terminal.
