"is it best to book directly with the hotel or use a booking service. My French is not up to the job of a direct booking."
I always like to deal directly with the hotel via e-mail, in English, unless there's a better deal or better cancellation policy via a reputable booking website like Hotels dot com or Booking dot com.
Most hotels do fine with e-mails sent in English - no need to use French. But keep it simple; here's my standard text:
I found your hotel in Rick Steves Provence And The French Riviera. I would like a single room for 5 nights, from 5 November to 10 November, 2015. Do you have a room for these days, and what is the price (paying with cash)?
Obviously, you modify this for your particulars. It's been a while since a hotel offered to reduce the price for cash, but I always ask, since for me it's no problem to use cash.
I title the e-mail Reservation Inquiry - Hotel Villa Glanum - St. Remy. Since I'm often reserving hotels for several different cities for a trip, it gets very hard to keep track of who's responding for which city; this way, it's right in the title of the e-mail replies.
When you get a reply, you have to reply to them to confirm the offer, and make sure you ask for a confirmation and receive it. Then, print out and take this confirmation with you, just in case.