Well here is my race report (very long - so skip if you want!)
I woke up early at 6am (having already woken three times in the night anyway) and managed to eat a bowl of cereal and half a bowl of porridge before nerves stopped me eating any more. My legs felt a bit achy due to the amount of walking I had done on Friday and Saturday (I'd tried not to do much but I think the stairs on the underground had got me!!) I double checked I had everything and then took a taxi to Charing Cross and caught the 7.09 to Greenwich. I met two guys from my club in Greenwich and we nervously walked past the red start to the blue start, admiring the rhino costumes on the way and we met up with another club mate and two local runners. The next hour or so to the start passed quickly and soon I was in pen 9 waiting for the starting gun.
I can't really remember the first 11 miles except for the great atmosphere among runners and spectators and me trying to keep to a steady pace (which worked as my fastest mile was 11.16 and my slowest 11.34).
I saw my parents, aunty and uncle at 11.5 miles and had a hug and a quick chat (but then had to wait ages for mum to empty her entire rucksack to find my energy gels - aargh!!). I had a quick stop and chat with my brother and his girlfriend at 15 miles and was feeling ok but very salty and warm.
By 16 miles there seemed to be more people walking than running and it was getting difficult to pass people in the narrow streets. I felt too warm and was trying to take on more water than usual. I remembered to run my mile for Len and it was great to see RW team 5 and get my extra gels.
At around 18 miles on Canary Wharf I started with a stitch and to feel sick so I had to walk for a few minutes until the stitch had gone. I think this is where I passed Arg from TOWIE!!
I couldn't get rid of the nauseous feeling and the stitch and so from around 19 miles I adopted a strategy of running at 11.15 pace and then walking at each mile point for a minute or when I needed to drink water (and I gave up with the gels). This worked ok as my miles averaged between 11.25 and 13.17 for the last 8 miles (except for mile 20 when I had a family pit-stop again). In the last 5 miles I was actually overtaking people and spectators shouted that I had good running form - which really spurred me on

By 25.5 miles I was feeling really sick and didn't know if I would have to walk to the end (I'd already worked out that I could walk the last bit and still do 5.30) but then an angel called Mel who was also running in an Alzheimer's Society T Shirt grabbed hold of my arm and told me to keep running with her - and I did virtually to the finish line!!
As I turned up the Mall I started to run as hard as I could but then realised this was a major mistake because I was going to be sick! I slowed down and manged to get over the line and pass the cameras but then I was really sick and had a marshall come to help me.
I felt much better after throwing up and was absolutely delighted with my time of 5.18.59 - a PB by nearly half an hour.
It was hard and there were times when just keeping going was an effort but the atmosphere was fantastic and I would definitely do it again