annette, I live in Devon, its not so much bristol i would worry about at the moment, but Taunton/Wellington area, Nr Taunton Deane services, traffic down to 1 lane and absolute nightmare, especially northbound on your journey home..
ps - tip -
if you are going cornwall via the A30 - try to avoid taking a pit stop at MERRYMEET/WHIDDON DOWN services, there are currently roadworks there, but the services this weekend were absolute chaos.
Stop off a little a bit further down on the Okehampton/belstone services. - quieter