They ran very, very briefly between Jan 2020 - March 2020 but I cannot recall if it was half-hourly or hourly from Paddington at xx15 and/or xx45.
Some other changes involved are:
1736 Paddington - Paignton service now terminates at Plymouth (missing out Maidenhead in the process as there's presumably less commuters to anger!)
Trains no longer detaching/attaching at Plymouth and running fully throughout to Penzance as 9 or 10-cars (I'm sure
@irish_rail will be moderately pleased!):
1004 Paddington to Penzance
1404 Paddington to Penzance
0910 Penzance to Paddington
1015 Penzance to Paddington
1615 Penzance to Paddington