I might have got that wrong - just looked on the NA site and the records might be at Lancahsire County Records Office after all, at:

Bow Lane
Preston
PR1 2RE
England

Tel: 01772 533039 Fax: 01772 533050
Email: record.office@ed.lancscc.gov.uk
Website: http://www.archives.lancashire.gov.uk
Open : Mon, Wed, Fri 9-5; Tues 9-8.30; Thurs 10-5; 2nd Sat of each month

This information, and the following, came from Access to Archives via the NA site:

LANCASHIRE CONSTABULARY
(Creator(s): Lancashire Constabulary)

"The main personnel records for Lancashire Constabulary are the examination books (PLA 11) and the record sheets (PLA 54). Indexes are available on the catalogue shelves, labelled 'Police Indexes: County'.
Although there is an 85 year closure on the examination books, and the record sheets are closed indefinitely, searchers can apply for a photocopy of an officer's record to be sent by post provided that the officer joined more than 85 years ago. For more details, see PLA 11 and the indexes.

"Other useful personnel records are the numerical registers (PLA 12), the photograph books (PLA 13) and pension and other records (PLA 14)

"General access arrangements: there is unrestricted access to police records over 30 years old, apart from personnel records as explained above. Also, any published items less than 30 years old (eg annual reports) are also open."