My 91 year old neighbour did a stint in the Ocean Weather ships in 1957 and he has given me the following:-
Flower class corvettes preceded the Castle class frigates. Britain maintained two Ocean Weather ships, India in position 59N.19W and another in Western Approaches.
Each O.W.S. stayed 21 days on station and had to remain within 25 miles of her allotted position: so the drill was, in order to conserve fuel, steam 25 miles up-wind of station, and then allow to drift 50 miles down wind, repeating the manouvre over a period of 21 days.
(My neighbour intends to look up some more details and he hopes to come up with this in due course.)