I had begun this design before I drew the Flower class and have finally gotten around to finishing it.
Given the importance of the North Sea oil and gas fields in my scenario all four of the planned Castle class are built but in my AU they are a more capable design, faster and longer with a hangar and a 76mm Oto to serve as useful patrol vessels in wartime.
In wartime these would probably receive a multiple Starstreak MANPADs SAM mount forward and perhaps a second Corvus.
Castle Class Offshore Patrol Vessel
HMS Leeds Castle, Castle Class, 1983
HMS Leeds Castle P265 October 1981
HMS Dumbarton Castle P266 March 1982
HMS Allington Castle P267 March 1984
HMS Dover Castle August 1985
Length: 305ft (oa), 281ft (wl)
1,985 tons (full load)
Two 3,500hp Paxman Ventura diesels
25kts on both
Endurance 10,000nm at 10kts
1x 76mm OTO Super Rapid
1x 30mm LS-30
1x Corvus flare-chaff launcher
Hangar for 1x Westland Westland Lynx or landing pad can accomodate a Westland WG.34 helicopter
Radars & Sonars
One Type 992Q air/surface TIR, one Type 1006 navigation.
*** Edit, thanks to Blackbuck for the new Lynx!