I fancy a Land Rover Defender 110 for WFP and was interested in feedback from any existing users out there re running costs
We get around 28mpg. Not brilliant but I doubt vans get much better. Once you factor in depreciation they are great value for money. I sold one this year for 3 times what I paid for it 5 years ago (I did get a bargain though). In general they do depreciate much more slowly than vans.
and what they are like generally to live with,
They are not exactly luxurious or comfortable but there are many after market things that you can get for them, it all depends on your budget.
size of tanls fitted etc.
There are 75l tanks that fit together nicely and fit right into the back of a Defender. Our 110s and 109s carry 450l that does 2 men about half a day using our system which has DI tanks fitted so you can top up anywhere. That would differ if you wanted a crew cab 110
Land Rover has a better image and would be more durable?
I bought my first Land Rover (a series 3 109) 10 years ago. It is used every day. It has done over 300,000 miles and is 32 years old. It starts first time every morning but does require routine maintenance. As far as image goes, it's hard to put a number on it but we definitely get customers as a direct result of not being 'white van men'. You get noticed.