Answer

By Country Walking magazine

Iceland's a fierce, weird and dramatic destination for walking and undoubtedly anything ambitious is best left to the climatic sweet-spot of July-September. Up until 21 September you can expect daylight comparable to the UK, but come October and it slips away quickly. Even the classic 4-5 day Landmannalauger to Skogar trek (the Icelandic equivalent of the Pennine Way in terrain difficulty terms) isn't advisable in October. 

It's not a complete write-off for walkig though. Dick Philips, who has guided walks in Iceland for 48 years, recommends you head for Hveragerdi, a town of 1200 souls (large for Iceland), 46km east of Reykjavik. Buses run here regularly from the capital and you'll find a good provisions shop and a tourist office. Most importantly you can spend time investigating the big thermal plateau, called Hengill, that lies to the town's north. Full of interesting terrain, and wild-feeling but nor really remote, the area's been taken over by the Reykjavik power authority, which has created a series of official walks around the plateau. Don't get the impression it's been turned into a civilised bit of parkland mind you. Says Dick: "It hasn't been municipalised any more than a Scottish bothy - just made nicer to use for those who go there. It's where I'd head out of season."

Thanks to Dick Philips of http://www.icelandic-travel.com/ and Sherpa Walking Holidays for their help with this Answer.