I dont Live in South West England but looking at the Transmitters in Service caption I would say between the Spring of 1974 and the Winter of 1975. . The Plympton Relay Near Plymouth came on the air 23rg November 1973 Followed by the Isles Of Scilly Relay which came on the air 3rd May 1974. The Next Relay Transmitter in the area to come on the air was Exeter St Thomas which Started Broadcasting on the 28th November 1975 which is not in the Transmitters in Service List above.
I dont Live in South West England but looking at the Transmitters in Service caption I would say between the Spring of 1974 and the Winter of 1975. . The Plympton Relay Near Plymouth came on the air 23rg November 1973 Followed by the Isles Of Scilly Relay which came on the air 3rd May 1974. The Next Relay Transmitter in the area to come on the air was Exeter St Thomas which Started Broadcasting on the 28th November 1975 which is not in the Transmitters in Service List above.