Jigger - I've also done Loch Ness - twice now 2004 & 2005. 'Quite hilly' is a good way to describe it - especially that long hill at about 17 miles! It must go down as my favourite, as the scenery is so good.
I'm training at the moment on 4 runs a week. I do a long run on a weekend - 14 miles now, but working my way up to 20/22 over the next few weeks. I do 2 lunchtime runs of 8.5 miles in Hyde Park; and I'll be upping this to 3 times a week soon - but maybe the extra one would be a bit shorter; plus 1 evening on the treadmill at the gym doing a Yasso 800 session - I'm doing 7:30 pace for the 1/2 mile, which is targetting a 3:45 marathon. Plus a bit of stretching and weight training, especially on my lower back. If I can keep this up without injury, I'm really trying for 3:45-ish. My PB so far is 3:51, so I hope it is achievable. I've been doing the long runs 30 seconds slower than target pace, and the shorter runs maybe 30-45 seconds faster. Does it work?? Ask me in April!!
TTKU - Is Siverstone good? - it's good if this is your first marathon as you'll get the feel of a 'big' race, but FLM is so much bigger. It's very wide open - two of the laps are on the race track. It's reasonably flat, which is good. The downside is there is not a lot of support - except in the stand by the finish. But if you like Formula 1, as you power down the finishing straight humming the guitar riffs from Fleetwood Mac's 'The Chain', you suddenly realise that Mr Schumacher would have finished his three laps about 2 hours earlier. It brings you back to reality....
Good luck to everyone with their fund-raising. Hope it all goes well.
