The battery on my 2006 Sport is in good condition. I am going to leave it parked up for 30 days (with alarms on?). How long can I expect the battery to hold out? Perhaps I do not need not have the alarms on full i.e.two pushes on the alarm button. Grateful for advice. Andrew Kennedy

If you are worried then a cheap solar panel that has a lead long enough to get to the jump start posts under the bonnet will trickle charge it fine. Make sure you get one with a blocking diode so you don’t turn the solar panel into a consumer in the night time though! I put a post up last year about how to rig the lead invisibly through the driver’s door jam and into the engine bay. In L494’s the battery is in the boot which is why you need to use the jump start posts under the bonnet.
http://www.rrsport.co.uk/forum/topic49141.html?highlight=solar
For L320 RRS like yours you can plug the solar panel into the cigarette lighter and put the panel on the dash top or the Centre arm rest if you have a sunroof. This all assumes the car will be parked outside of course!
Provided it isn’t going to be really cold outside then you might get away with 30 days, I used to leave my L320’s parked up for 12 weeks at a time with the solar panel charger on and for more than a month without in the summer, never could get it to stay charged that long in the depths of winter so got my brother to drive the car monthly 2020 Pangea Green 1st Edition D240 New Defender 110 is here and loving it
2018 Melting Silver Mini Countryman PHEV - soon to be replaced
2015MY Corris Grey SDv6 HSE Dynamic, the best car I have ever owned, totally reliable only a cou0le of rattles in 3 years, now no longer in my care
Also in my garage is a 1996 TDi300 Defender 90 County HT made into a fake CSW