In reply to jon:
> I put one of these on mine, they are good chargers and a common conversion use, similar load to yours, no problem:
> You might get away with a 7A one
> //www.12voltplanet.co.uk/victron-energy-blue-smart-ip65-charger-12v-7a-bluetooth-built-in.html 2
> The non Bluetooth ones are cheaper if you can find one
I have the IP22 which is likely to do the same job for you as the IP65 (I probably would have got the IP65 instead if it has been in stock). I use it to top up the battery if needed in the winter when the solar panels may not contribute much. Can also be used to charge the vehicle battery if you ever accidentally drain it (may require you to switch charging settings depending on your is setup which is easy to do).
The Bluetooth is an unnecessary feature in my opinion if you can get a non Bluetooth version, particularly as the Bluetooth range is very limited. Might as well just look at the lights on the unit.
You can get them cheaper than from 12volt planet, but check which cable fittings they come with as many of the cheaper ones will come with a 2 pin European plug. The 12volt planet ones come with a 3 pin UK plug. Also worth noting is that the IP65 should come with cables to connect to your battery, the IP22 does not so you may have to factor in £5-10 for those of you don't already have them.
If you are ever unsure whether a product is suitable for your setup, the phone and email support from 12volt planet is top notch, worth paying a little bit extra for in my opinion. They are amazingly patient with basic questions but also have the knowledge to answer far more complicated queries.
I assume you have some way of reading the voltage and current in your leisure battery? If not, get a voltmeter from Screwfix. They are about a tenner and will confirm whether the battery charge and/or health is the cause of any problems.