Glad you got it running. Watch that battery though, once you let them go down to 11.9V they are essentially damaged, lead-acid batteries dont like deep discharges.
Mine now has effectively 1/2 its original capacity or less. It will charge to 12.7 and pretend its fully charged, but as I recently read this is a surface charge which quickly drops to true voltage when you apply any small load. Mine quickly drops to 12.4 ~ 12.3V.
My S8 seems to crank longer the lower the battery voltage.

Interesting.

Went on holiday during the 'summer' and unfortunately, left a phone charger plugged into the fag lighter.

This flattened the battery utterly and completely.

Although it took a charge, maybe that buggered the batt?

I just go by what I read on the web, for example:
http://www.batterystuff.com/blog/how...ry-is-bad.html

Observation with my own battery, I charged it for 12 hours with a basic model Ctek charger, fresh off charger it read 12.7V. I put a 10A load on it for 10 seconds, after which it read 12.4V. That is not right if battery is ok. It should not go down to 12.4V after a 10 second 10A load.
I charged it a second time for 14 hours using de-sulphation mode and the result was same as above.

Apparently lead-acid batteries are not supposed to spend a long time below 12.4V, mine has and has lost capacity.
http://www.tayna.co.uk/tutorials/car...ur-battery.php