Findmypast.co.uk has passenger lists for ships departing from the UK beginning in 1890. What about dates before 1890? Do the records exist anywhere? I'm particularly interested in departures to the US in 1855.
The FMP lists come from series BT27 at The National Archives (for the UK, at Kew). The Catalogue notes for BT27 say "Lists earlier in date than 1890 have not survived."
- The document guides describe stuff at Kew, which is not generally on-line (not surprisingly);
- If anyone else picks up references in this query to ships leaving the UK and gets interested, be aware that lots of voyages from 1890 on were not recorded in the BT27 ledgers. All traffic between mainland Britain and Ireland was excluded (initially this was internal to the UK) as was purely European traffic.
As you mention the time period 1855, did your ancestors originate from Scotland? The Highlands and Islands Emmigration Scheme assisted 5000 people to emmigrate from western Scotland to Australia. The online database is at http://www.scan.org.uk/researchrtools/emigration.htm
Consider why the people emmigrated. Although passenger lists may no exist, records associated with the reason for the move may still exist eg assisted travel, criminal transportation, colonisation.