No, 387301 was reported going to Paddington back in December. Not 387306 though.Was this the first solo ex-C2C 387 from Paddington? 4-car service to Theale.
Realtime Trains | 1K04 0807 London Paddington to Theale | 19/03/2022
Real-time train running information for 1K04 0807 departure from London Paddington to Theale on 19/03/2022. From Realtime Trains, an independent source of train running info for Great Britain.www.realtimetrains.co.uk
387306 looks like it’s on a diagram all day.
https://www.railforums.co.uk/threads/gtr-to-loan-6-387s-to-gwr.219662/page-6#post-5435169