Motorhome newbie - Hymer B544SL queries

Hi

I am a newby to the Motorhome scene - currently have an Hymer Feeling 425 caravan - and wondered if anyone can help with a few queries regarding a 2008 Hymer B544SL we’re about to buy.  

Bear with me because I’m not a DIY handyperson by nature, so your advice would be gratefully received:

1). When hooked up to the mains does this power both the vehicle and leisure batteries via what I’ve seen described as a 'split charge relay' - does the Hymer charge on this basis so that I can charge both batteries?

Despite the 4 locking point mechanisms on the Hymer, when looking at door security I would appreciate advice on external or internal locks or other options that ideally, don’t require me to go through the external wall of the van as my partner insists any secure needs to be as discrete as possible as well as the risk of me with a drill and a homemaker!

2).   For the single cabin door could anyone suggest suitable internal locks - would the Milenco van internal cab lock doors do?

3)   Could I use that cab lock to secure the locker door that gives access to the interior of the van via the sofa to provide further security to that locker door?

4).  For the habitation door would something the Fiamma Safe Door Frame Lock be easy to fit while giving necessary security.

Thanks in anticipation of any advice.