A search of the National Archives Catalogue has revealed the following references to HMS Rushen Castle:

ADM 217/586 * HMS RUSHEN CASTLE: report on proceedings of convoys SL.172 and MKS.63 escorted by B 21 group from 16 October to 25 October 1944 - see also Convoy Web

ADM 217/587 * HMS RUSHEN CASTLE: report on proceedings of convoys OS.90 and KMS.64 escorted by B 21 group from 2 October to 4 November 1944 - see also Convoy Web

ADM 217/588 * HMS RUSHEN CASTLE: report on proceedings of convoys OS.93 and KMS.67, escorted by B 21 group from 25 October to 1 November 1944 - see also Convoy Web

ADM 217/589 HMS RUSHEN CASTLE: report on proceedings of convoys SL.175 and MKS.66, escorted by B 21 group from 7 to 15 November 1944 - see also Convoy Web

ADM 217/590 HMS RUSHEN CASTLE: report on proceedings of convoys OS.96 and KMS.70, escorted by B.21 group from 23 to 27 November 1944 - see also Convoy Web

ADM 217/591 * HMS RUSHEN CASTLE: report on proceedings of convoys SL.178 and MKS.69 while escorting B.21 group from 5 to 12 December 1944 - see also Convoy Web

ADM 217/592 HMS RUSHEN CASTLE: report on proceedings of convoys MKS.77 from 15 to 21 January 1945

ADM 217/593 HMS RUSHEN CASTLE: report on proceedings of convoys OS.110 and KMS.84 from 11 to 20 February 1945 - see also Convoy Web

ADM 217/594 HMS RUSHEN CASTLE: report on proceedings of convoys MKS.85 from Gibraltar to United Kingdom from 24 February to 3 March 1945

ADM 217/595 HMS RUSHEN CASTLE: report on proceedings of convoys OS.120 and KMS.94 from 5 to 8 April 1945 - see also Convoy Web

ADM 217/596 HMS RUSHEN CASTLE: report on proceedings of convoys MKS.95 from 15 to 21 April 1945

ADM 217/597 HMS RUSHEN CASTLE: report on proceedings of convoys MKS.98, supported by close escort, and group 31 from 5 to 7 May 1945

MT 15/1386 `Weather Surveyor' ex HMS `Rushen Castle', Castle class corvettes conversion to weather ship 1943-1962

An explanation of the reference numbers is as follows:

ADM  Records of the Admiralty, Naval Forces, Royal Marines, Coastguard, and related bodies

Division within ADM  Records of Stations and Fleets

ADM 217  Admiralty: Western Approaches, Station Records

MT  Records created or inherited by the Transport Departments and of related bodies, and of the London Passenger Transport Board

Division within MT  Records inherited and created by the Ministry of Transport and successors, Marine Divisions

MT 15  Board of Trade and Ministry of Transport and Successor Bodies: Consultative Marine (M, CB, and CM Series) Files

All of these are worth looking at - they are included here in case someone else has an opportunity to visit The National Archives before I do!

In Chapter XVII of his book, "Really Not Required", Colin Warwick records the following:

"In June 1944 the southbound Gibralter convoy, escorted by B-2 Escort Group, was halfway across the Bay of Biscay when the two H-class destroyers with the two Captain class frigates received orders to detach themselves and head north, in advance of the Allied landings in Normandy, with the knowledge that German U-Boat flotillas on the French coast would be thrown into the battle.  Rushen Castle was ordered to take over as senior officer, and on return to Liverpool I became the Escort Group Commander."

I imagine, therefore, that the above reports will have been prepared by Colin Warwick in his role as Escort Group Commander.  I understand from a reference towards the end of "Really Not Required" that Colin Warwick was the only reserve officer commanding an escort group in the Western Approaches Command, all the other groups being under the orders of Royal Navy commanders. 

* Links added to Reports of Proceedings as they are transcribed and added to this site.