Get an Optimate, it's what we use on the bikes over winter, they come with a connecting plug so you leave the short wires attached to the battery terminals And it's easy to just unplug it
We use a CTEK_xs3600 and leave it on all winter. There is a larger one for bigger batteries but we find the xs3600 OK if we don't let the battery go down too far in the first place. The CTEKs are for maintenance and charging and are very good indeed.
You need to fit a "battery mate" type device, available from CAK tanks. They are easy to fit, or get a auto electrician to do it. When on EHU you charge the leisure battery until it reaches aprox 13.6v then the device will switch to trickle charge your starter battery,it will charge back and forth, maintaining both batterys safely.Your Autoquest vehicle is unable to do this at present,they did not fit this kind of device.
I use a solar panel, supplies enough current, at least buy one that will give enough current, to trickle charge the battery throughout the winter. No trailing mains to motorhome.
I fitted a 120 watt solar panel on my motorhome and even when it is parked in the garage with a polycarbonate roof which is not clear it keeps 2 110amp leisure batteries and the engine batterie fully charged.
If you do go down the smart charger route ( Optimate, Ctek etc ) to charge the engine battery it is possible to connect them directly to the battery with the battery still connected to the vehicle, as the ctek blurb says connect and forget. Make sure the model you go for is suitable for the amphour rating of your battery. Ie the Optimtae 4 is only suitable for batteries up to 55ah, ie motorcycle batteries and the like, other models go up to 110ah and the new ctek beyond that. Not wishing to teach my grandmother anything.........a standard non smart charger and some of the ultra cheap so called smart chargers should only be connected to the engine battery with one or both of the of the vehicle battery leads removed to avoid damaging the alternator.
I emailed optimate years ago to ask if I could use my optimate 3 (made for small motorcycle batteries) on my Land Rover defender battery. The reply was that the only difference would be that the charge part of the cycle would be longer but otherwise ok. I used it on my Defender for about 3 years with no problems at all. It still works to this day but is now connected to my Honda Scooter.