If your lead fits directly, that’s fine, but you may also need to insert a short adaptor lead to connect your UK lead to the bollard. In France this will probably be a Schuko so the adaptor lead will look like this (Pic 1).
Alternative connections may be used in other countries, although the Schuko connection is designed to work safely with both a reversed pin earth connection, and a side contact earth connection.
Once you have a UK spec socket to check, use this second adaptor lead (Pic 2) to temporarily convert to a standard 13A domestic socket.
You can then use a plug-in tester such as this (Pic 3) to verify the polarity of the supply.
If the polarity is found to be reversed, then a crossover lead (Pic 4) needs to be inserted in line to swap over the line and the neutral cores, before re-checking the polarity.
If you do not have a crossover adaptor you can alternatively, with care, make the change by swapping the brown (Live) and the blue (Neutral) wires at one end of your extension lead (Pic 5). Obviously DO NOT do this with the lead plugged in.
Once the 16A plug is reassembled, mark the lead clearly to indicate the change you have made. At the end of your stay on site, restore the lead to its standard configuration and remove the warning label.
Once the polarity is correct, then you can remove all unnecessary adaptors and connect your electric hookup lead from the caravan to the EHU bollard, remembering to plug in the caravan end first. Finally for confirmation, plug your polarity tester into any socket in the caravan, to confirm the polarity before turning on any appliances.