These ships were large, 10 year old USCG cutters, transferred to the RN for patrol duties for which they were very suitable, and also to allow the USCG to replace them with new cutters.
Although they were shorter than contemporary RN sloops, they were deamier and deeper and so were excellent sea-keepers, despite only having a single screw.
The propulsion was novel for the RN, a single turbo-electric system meaning complicated gearing and a long shaft was not needed, and power could be controlled direct from the bridge - very advanced for the time.
In 1942, armament comprised of;
1 x 5" and 3 x 12pdr in Banff, Fishguard and Walney;
1 x 5", 1 x 12pdr and 2 x 2pdr in Gorelston and Landguard;
1 x 4" and 3 x 12pdr in Hartland;
1 x 4" and 1 x 12pdr in all other survivors.
All ships carried four single 0.5" and six single 0.303" machine-guns, SW type 273 and AW type 281 RDF.
In 1943, armamaent was modified to;
4" and not 5" guns, and 20mm and not 0.5" MG guns in Banff and Fishguard;
2 single 2pdr and 4 single 20mm AA as light armament in all the rest apart form Gorleston which carried 0.5" MG and not 20mm AA.
Again in 1945, armament was changed;
to one 4" and one 12pdr in all ships, apart from Fishguard and Gorelston which had a 40mm AA instead of 12 pdr;
two single 2pdr AA in all, 7 to 4 single 20mm AA, 6 single 0.303" MG's and four DC mortars with 100 DC's aft.
They were extremelly active during the war, being large, seaworthy, comfortable and well armed and loved/

Pictures of ex- USCGC type Patrol vessels

Walney at sea. Note 5"/51 LA gun up for'ard and just abaft the superstructure