Service areas M5

ggregu

Hi, I'm about to set off on my first major trip next week going to Devises first for 7 nights and then down to Mevagissey, Cornwall for another week. I have been looking at service areas for stopping on the second leg of the journey ie south of Bristol And
down into Cornwall. As I am going on my own but with 2 small dogs who require regular tiddle stops I'm a bit anxious about where to stop, do all service areas have designated caravan areas, and can I park in the lorry area if not? Any advice or suggestions
of stopping areas would be very welcome. Thanks. Gill