FlightSim.com but I bought the Lukla and Twotter direct from the Aerosoft site and I went for the discs not the downloads, I like to get my hands on the real goods!
Had a wee jaunt with the Twotter EDI-INV-WIC-KOI-LWK t'other day as I had a wee bit of time on my hands. It was a route Loganair used to do with the aircraft many years ago and I'd travelled it a few times. Used the real weather 15min updates option which was real fun it got a bit choppy after INV.