Hi Uisa,
thank you for your response. Unfortunatelly, I have not found anything by now. I already contacted the MCS-aware forum in the UK and they put my request in one of there newsletters in order to spread it to all their members. Sadly, I received no response until today. I also contacted Breakspear hospital hoping they could aid but they offer their scent free guest rooms only to patients' relatives.
No matter to whom I talk to, everybody tells me that England is even more underdeveloped regarding MCS than Germany.
Thanks a lot for the link to organicholidays. Maybe I will find a tolerable accomodation there.
I would be gratefull for any more information that could help me to find a place to stay. Moreover, I would be fine with travelling up to one hour to London city-centre so that the flat could also be a bit out of town.
Christian