Yeah it's a standard one. I've just realised that I didn't earth the leisure battery.
Would this of made a difference?
That certainly would make a difference on. A normal install.
However, if you also have a start / stop, really a battery to battery charger unit should be used instead. If you do not, it is unlikely to give the system a reliable charge. Modern vehicles featuring start/stop technology / regenerative braking / and smart alternators cause the voltage to drop and increase when required or not required. This means the standard SCR will shut off when the alternator turns off, thus causing your system to not get a sufficient charge.
You can get around this by always keeping your lights on / radio etc when the ignition/engine is on to create some drain on the battery thus keeping the alternator on for longer. This obviously is not ideal so thus why we recommend our battery to battery charger unit on any vehicles registered 2015 onwards.