You will need to find out what the Setec that is in your Base station pulls, I would be surprised if a 300w generator would be up to the task I know my 25amp Projecta charger has the potential to pull around 700w or more.
You may get away with a 300w genie and a small battery charger connected directly to the batteries but this may not be enough supply to keep your batteries over the 50% mark depending on what you are power you are consuming of course.
More info would be good battery size, length of stay off the gird, what you will running whilst off the grid etc. I'm thinking you may get away with a small battery charger and LED lighting but that would be about all.
I'm not a sparky but I am curious as to why it has a 230v power outlet instead of a 240v? does this matter I don't know maybe there is a sparky on here that knows.
The other thing to consider if you are going to use a generator to power your van is the fact that the RCD may not work, if you are going to do this on a regular basis I suggest you have an electrician replace the RCD with an RVD as these will function whilst using a stand alone power unit.
