F241 on the left could be HMS Kale.
According to
https://www.worldnavalships.com/directory/shipinfo.php?ShipID=2355 her details were:
Name : HMS Kale
Laid Down : 22nd September 1941
Launched : 24th June 1942
Completed : 4th December 1942
Type : Frigate
Class : River
Builder : Inglis
Country : UK
Pennants : K241, F241
Fate : Sold for scrap November 1956.
There were four vessels with the Pennant F21, so the only contender should be HMS Dart. Judging by the lack of superstructure on the fore deck, she's in the process of being dismantled. This was completed in 1957, according to Wikipedia.
Name : HMS Dart
Laid Down : 8th September 1941
Launched : 10th October 1942
Completed : 13th May 1943
Type : Frigate
Class : River
Builder : Blyth Shipbuilding and Drydock Co. Ltd.
Country : UK
Pennants : K21, F21
Fate : Sold for scrap November 1956.