I confirm that Ordnance Survey does not hold the information you have requested. This is because we do not hold historical mapping between 1955 to 1961 to be able to confirm whether or not XXXXXX was attached to XXXXX at that time.
However, under the duty to provide information and assistance in accordance with section 16 of FOIA, we can provide the following information which may assist you in this matter.
You may wish to contact The National Archives (TNA) in the first instance as OS transferred its historical mapping to TNA for archiving. Details on how to contact TNA can be found on their website or alternatively their address is The National Archives, Kew, Richmond, TW9 4DU (Tel: 020887673444).
The National Archives may hold historical copies of maps/plans for the period you request, along with records of items which may be held elsewhere such as the Libraries and Archives departments of:
Lancashire County Council, information on how to contact them is available on their website and their address is County Hall, Fishergate, Preston, PR1 8XJd.
Liverpool City Council, information on how to contact them can be found on their website and their address is Municipal Buildings, Dale Street, Liverpool, Merseyside.
Historical mapping is mapping that no longer reflects the situation on the ground at the time of the last survey. OS website provides useful information on historical mapping, where you can buy it and information that is accessible in various archives.