So to put is very bluntly if a pilot without a life raft has an engine failure over water the chances are he will die in the water even in the summer, in the winter this death is likely to take less than 15 min.
SES can supply a very light single man life raft ( the type that fits into ejection seats) I would think that the limited space on a micro light would not preclude one of these.
Survival Equipment UK | Parachutes | Ejection Seats Servicing | Liferafts