First a double circle double-arc "PORTISHEAD / BRISTOL" cancel from 1936, although the circles are not clear. The envelope was addressed to "The Hospital, Amsterdam" but the addressee was not found so it was returned to Portishead.
Next a Field Post Office registered envelope to Portishead with a "PORTISHEAD / BRISTOL" single ring receiving mark from 1946. The sender was in Schleswig Holstein.
And finally a BT Maritime Radiotelex envelope from Portishead Radio, Highbridge, with a "HIGHBRIDGE / SOMERSET" meter mark from 1989.