Went to the top with a group tour about 10 years ago in June time. Hard work going up , 3 days I seem to remember of nothing but ascent. Got mild altitude sickness at the top. We came down via a scree run, basically over the side of the mountain and don't try to stop. Don't drink the street...
Was there about 20 years ago, visited 4 islands, one of the best holidays, whale watching was superb, lots of great walks, no beaches (a good thing), swim off the lava. Weather can be unpredictable, pouring tropical rain and hot sun on the same day.
Was in Western Sicily 2 weeks ago, stayed at a fab old abbey Abbazia Santa Maria del Bosco, great if you like history and quiet. Went to Erice which was nice but tourist hotspot. Palermo was busy, several sights to see, especially the Theatre. 2 full days was enough. Day trip out to Cefalu by...
Another vote for DIY, easy via the gov website unless you have any special circumstances, no need to pay >£500. Try the website, no cost unless you submit the applications (which have to have wet signatres)