Andrew, Ben: Absolutely I want to get some practice actually running in the Lakes, but I can't just go up there every weekend like I could back when I lived in Manchester. I'm concerned about the January recce day because on the page "Recce weekends, the basics explained" it says, regarding the sections that are on the 100 route, "Things to note are that these sections are tough and may be done in darkness. Last year during the recce of section 1 (due to take place in Jan) runners were still finishing at 8-9pm in the evening, completing Blacksail Pass and Scarth Gap in darkness. For those of you not familiar with the Lake District, those climbs and descents are not for the inexperienced.." So, I just want to avoid trying to do too much too soon and overfacing myself. I am going to get in some practice night running over the next few months. I'm already increasing my hill work, and I'll be planning days out walking on hilly terrain as well.
booktrunk: I trained for my first 50-miler (NDW50) this summer by basically following the Ultraladies 50 mile training schedule. There are others around e.g. there's one on the RW USA site. So, back-to-back long runs, yes, but back-to-back marathons, not necessary. I'd advise starting by say adding a 6 miler the day after your 18-mile long run, and work up from there. At present I'm trying to keep "ticking over" for distance by doing a 20+ then a 10-12 about every second weekend (e.g. 21 + 11 this last weekend). From what I've been reading, training for Lakeland 50 newbies emphasises "time on feet", so long days out walking are recommended as well as time running.