From the above it looks like next door owns the alley (provided no change of ownership has taken place) and your property has a right of way over it subj to contributing to repair.
You can check who owns the actual piece of land by doing an index map search at the Land Registry (free for under 20 titles found).
This is the form...
http://www1.landregistry.gov.uk/assets/library /documents/SIM.pdf
You will need to put a plan with it, preferably to a proper scale eg an ordanance survey plan.
You can find the appropriate Land Registry on the title register you have and address details on the form here...
http://www1.landregistry.gov.uk/regional/offic es/
Please note though that it will only show up registered titles and will only give you a title number though you can then order a copy of the register and plan for �6.
Make sure you mark the plan clearly inc ase it picks up on a neighbouring title number.
Hope this helps.