It would seem that the puddles issue is by design and will not be fixed by codemasters
Below is the reply from codemasters regarding the issue of no puddles or reflection during a wet race.
Thank you for submitting your recent request to Codemasters Customer Services concerning F1 2010.
Thank you for your comments, we have passed them on to the producer of the game and our design team. However the rain effects have been reduced with the patch as it was felt there was too much standing water present on the track.
If you need further assistance, please reply to this email and INCLUDE THIS LINE IN YOUR REPLY:-
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Or include the entire text of this email.
Kind regards
Rob
Codemasters Customer Services