No he wasn't born here, he was born in Somalia. However, he has a British Passport and has had for many years... he is therefore British. He has lived here since he was 8. He is 31. I'm happy to call him British if he is. Or Somalian-born Brit if we are being picky... but that is a bit of a long winded effort to be honest.
Dehydration can make you feel nauseous. I have often felt rough after a long run if I am dehydrated as I haven't drank enough during the run. It can be a combination of this.. while low blood sugar can make you feel sick/dizzy. If you get cold that can also exacerbate symptoms.
The answer to your question re marathon shape in 9 weeks with no exercise in the last 4 months is no. But I think you know that already.
I am assuming by "this year's marathon" you mean erm.. London??? You are aware that there are a billion other marathons throughout the year in the UK that you could train for when fit and not struggle to walk around with an injury. It might even save you a fortune be a load less crowded and probably be a hell of a lot more scenic. But then I've never understood the fuss about London.
Aw man I LOVE XC!!!! Yeah sure it's cold, wet, miserable, muddy and you run around hyperventilating like a chronic asthmatic feeling like your lungs are going to explode and wondering why your legs feel like lead and when the measly 4km (or whatever distance) is going to be over.... but then you get to the end and realise how much FUN it was to splash in all the mud and puddles... all the while actually coughing up your lungs. Changing in the open sided tent afterwards is the least of my worries The guy in our club who deals with the XC always tries to arrange extra mud for me It's my favourite time of year... and it coincides with cyclocross season which is like the same thing... on a bike which isn't too far from a road bike in appearance ... Did I say I like MUD???
Wenterrapin... nothing scenic about running in and around a suburban country park/schol playing fields or similar...