Hello Margret
The Bailey web site list the current 550/5 with an MPTLM of 1271Kg, and my sources suggests that all models of the 1.5dci scenic are rated to tow up to 1300Kg, so technically there is a match. However, the margin is only 29Kg, which can easily be swallowed up by manufacturing tolerances of the caravan, moisture content in the wooden structure or last minute nick-nacks.
However the actual ratio depends on kerb weight of the car that is determined by the year, engine and model of scenic. Again my sources suggest that the worst-case scenario would be 95% and improving to 87% for the 2004 Grande Scenic 1.5Dci
Damian has also pointed out an important consideration to do with Gross Train Weight. Renault have been quite meagere with this figure for some models, and it means you cannot fully load both the car and trailer to their maximums as the would exceed the GTW. I have no information for the GTW of the Scenic - speak to your Renault Dealer or check your owners handbook or data plate.
It is a sensible suggestion to keep the ratio as low as possible, and the CC give 85% as a guideline especially for novice towers. Legally provide you passed your test before Jan 1997 you can tow up to maximum permitted by the cars manufactures, otherwise you are restricted to a maximum of 100% or the manufactures limit if it is lower than 100%
Do not rely on data supplied through this forum as being accurate, it is usually gathered from multiple sources that from time to time have been shown to include some inaccuracies. Always check your data from the manufacture or authorised dealer, and the Department of transports sites.