1. You presumably have a long lease of your flat, as does the downstairs owner (X).
2. This reply deals with X and his leasehold. That someone else occupies is irrelevant- he/she could never have more rights than X has.
3. The leases will state what rights ("easements") benefit each leasehold.
4. Does X have any easement from the alleyway through the gate and your garden? If not, does anyone else? Read your lease carefully.
JEFFREY SHAW, solicitor [and Topic Expert], Nether Edge Law*
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2. Telephone advice: see http://www.landlordzone.co.uk/forums/showthread.php?t=34638.
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