I confess I used it a couple of times in July, especially after I got it fixed at the last service, but in the 3 years I have had the XS I have rarely used it.
I recently bought some these vent demister thingies after I saw the chap at Newbury
NEW PAIR Land Rover Defender side window + windscreen demister 90/100 TD5/300TDI | eBay which woork quite well at clearing the side windows.
As for demisting in winter, I have never really found a/c to work in the 'fender, given that the A/C in a TD5 is a completely seperate unit to the heater. so your knees freeze while the feeble heater just gives up trying to heat the chilled air.
Remember that the A/C is an internal recirc device whereas the heater relies on sucking external air through the heater matrix, so unlike a modern (puma) unit you can never really dehumidify the air.
As for the leather seats, fortunately when I got my 110 XS it had seat covers which I have never removed, ergo I have never even seen the leather as I am frequently filling the motor with crud for the tip (or at least swmbo does)
The heated screen is a fairly good device when they work properly, but mine does tend to work in patches, ironically clearing a 1ft strip right in front of the driver last (The main stealer refused to look at it as it was not covered by LR extended warranty)
In summer I just open a rear window and the front flaps as previously indicated and it defugs the 110 quickly. Dont know how Puma drivers live without the flaps. The dog loves sniffing through the dash when they are open too.
I would recommend fitting heated mirrors though as they are great at clearing spray as well as frost.