The operational rules and mechanics of the gilt market are set out in the documents available here.
GEMM Guidebook - A Guide to the Roles of the DMO and Primary Dealers in the UK government bond market is aimed at the DMO gilt market counterparties and outlines their obligations as gilt-edged market makers and the DMOs obligations to them.
The Information Memorandum - Issue, Stripping and Reconstitution of British Government Stock sets out the legal details behind gilt issuance, while Official Operations in the Gilt Market - An Operational Notice provides detail on the operational procedures conducted by the DMO in the gilt market. Finally, a comprehensive background paper by the Bank of England on the gilt strips facility can also be found here.
Documents relating to previous versions of operational rules and other historical information are available here.