Grob Driver, like yourself I thought exactly the same - that FPL's by the fact they are filed within 24hrs of the intended flight do not require a date. A couple of years back Shoreham ATC politely pointed out that I should put the date of the flight on the FPL if filing the day before (I had the same conversation with them about the logic of the timing - I thought the 24hr "rule" was so the flight time was not open to misinterpretation). Since then I have entered it in the remarks field of the CA48. I always fax them direct to Heathrow NATS (0208 745 3492).
Hope you have a good trip to LFAT. If its any help for weather info' you should phone the ATIS recording on 0033 3 21 05 51 26 as LFAT does not appear on the TAFs / METARs
Be aware that the airfield is particularly prone to fog which can come in very quickly.
Let me know if you want any other info,'
Best Rgds
Rich