If there is one thing the M4 corridor isn’t short of, it’s rapid chargers.
After Leigh Dalemere going east there is Ionity and MFG at the next junction, accessible both ways, a bit further down is instavolts and V2’s at Membury just the other side of Swindon.
There shouldn’t be any need to do any ‘painful’ loops of the M4 unless you are wedded to tesla rapids.