New info: next week OVH will add again an option for big databases... If it is not too expensive it would be the easiest solution until IMCDB can have its own server (anyway, for that the problem is not the cost but the fact that I cannot manage a Unix/Linux server myself).
If we can have a 100 or 200 MB limit, it will allow us to keep the current system at least until 2008 or 2009