Hi Tim and Ian
Tim, it took us 10 days to get the visa from scratch. We're both travelling on British passports. Ian, costs in Tunisia were high, compared with elsewhere we've been, but still affordable in terms of what you might pay for the same in England. Camping outside Tunis was expensive, but if you cook for yourself, you can keep the costs down. Difficult to refrain from all the lovely pastries, though.
We were issued with a transit visa for 10 days, starting from when we entered the country. Because of money and time constraints, we took 4 days to travel across. On the whole, accommodation costs (only hotels, no campsites in towns along the coast and as 2 lone girls, we elected not to bushcamp) were quite low, but food was a little more expensive. However, the cost of fuel (about a tenth of what it cost in Tunisia) more than made up for that! Libya was fabulous, albeit our journey was quick and only along the coast. We were treated with such kindness by the locals, who were very helpful with directions.
Beware that ALL roadsigns are in Arabic only and you'd do well, when planning your trip, to have an Arabic translation of each town you're planning to pass through or stay in. It's not always easy to work this out from the mileage on the signposts, as they don't always correspond to your maps. We asked one of many kind people to write down the Arabic names and managed that way, although allowing for the idiosyncracies of an individual's handwriting made this a challenge too!
Enjoy
Bel