The process to collect your pack was straight forward. When you entered the Expo, you went to the first desk to collect the pack - race number, instructions explaining the details for Sunday, large kit bag and a sticker for the kit bag with your race number on it - then you went on to the second section to collect your timing chip which was paired to your race number.
After this you could then go into the Expo to browse around the various things on offer (mainly retail). The most useful stand for me was the Lucozade one as they had timing bands for various target finish times showing the time that you should be on as you pass each mile marker.
This would prove useful in the race as there are a few underpasses along the way that block GPS watches so the distance is no longer accurate.
On the way out of the Expo, runners were given a small goody bag with a few leaflets and food based items.
We have relatives who are close to Morden tube station so stayed with them overnight and was on the tube around 0730, arriving at Waterloo shortly after 0800. Everyone running gets free access to the TFL network on the Sunday - you just show your race number to the person at the gate. From Waterloo there is was a short walk to Waterloo East to get the train to the Blackheath blue start point.
Compared to the Tube to Waterloo which was nearly empty, the train from Waterloo East to Blackheath was standing room only. Speaking to a few people in the staging area later on who arrived later, they had to wait for 3 or 4 trains before they were allowed on one so the trains before 0800 appear to be quieter (the disadvantage being that you have to stand around in the staging area for longer.)
Your start pen is allocated based on the finish time you predict when you register and is designated by a smaller number on your race number. Once in the pen you can move around to whichever location you like but the further forward you can go the better. Certainly aim to get ahead of any pacers in the pen as they are surrounded by a wall of people in the race which is very hard to get past once the race starts.
There are a few differences compared to a 'normal' race as well:
The sheer number of runners. At the start of most races, there is a bit of congestion as everyone finds their place and gets into their pace before the field thins out. At London, this sort of congestion is pretty much for the whole of the race which makes it difficult to settle into any sort of rhythm and make up and time that is lost due to it.
When the red and blue starts merge around mile 3 it seems customary to boo each other as well - probably because if the field looked like it was about to thin out, the merge soon puts an end to that :)
Spectator support. For pretty much the whole course, there are spectators lining both sides cheering the runners on and various bands and DJs providing entertainment along the way as well. If you have your name on your top then people will cheer you on as you pass them as well.
Someone on the London Marathon Facebook page also highlighted (after they had run it) that the St John Ambulance people along the way that hold their hands out have Vaseline on their gloves and not some sort of fancy energy gel so its best not to eat it like they did...
As for the race itself, I remember going round the Cutty Sark, over London Bridge and a few landmarks towards the finish but most of the time you are focusing on picking your way through the traffic so you cant really relax and really take it all in. A bit of a shame given how difficult it is to get a place to run it but that applies to most races really.
Would I do it again? Yes (I have put my name in the 2016 ballot). The atmosphere is different to any other race and the organisation is first class as you would expect. I also am grateful for being given the place through the Club as its one ticked off the bucket list. Plus the changes to the ballot system for 2016 will probably make it harder again to get a place in the public ballot.