Car seat for 21 month old - he hates being in it - help!

[joyjoyjoy]

My 21 month old ds hates being in his car seat and always wriggles out of the top straps which is obviously dangerous but I can't stop him doing it. On top of that he hates being in the seat and isn't easily distracted - not interested in the DVD players we have for the other two DS. So he screams a lot. We go on a lot of long journeys and are planning on driving to sw france in the summer but i can't face the journey with him shrieking in the back seat. Any thoughts? any car seat recommendations or devices to stop him getting out of the straps? (I have a feeling such devices are illegal though...)
thanks

The cheapest suggestion is after you have checked that the straps are at the right height and are tight. Make sure he doesn't ware a coat in the car as this can make it difficult to tighten and make it easy for him to get out of. When he gets arms out stop and don't drive until he put them back in. The other option is to get this car seat they are not cheap but you won't need to buy another seat.
www.kiddy.de/gb/comfort-pro Which also said they were the safest carseat in thier test