Hi Andy
The english BDM records are very different to and not as useful as the Scottish ones. There are various different groups transcribing the England/Wales indexes which makes finding the records you want easier, but there is nowhere you can download the certificates. You can order them online from Gro and they can also be ordered from the various county offices, some of which are online. Information on the certificates is very limited, death ones in particular - they do NOT show parents.
When all other searches fail, trawling the images at ancestry (and I think another site has them - used to be called 1837online ) is the only way to check the full list online - and this is not guaranteed to have everyone. It is also slow if you don't know the year, but not as slow as you intially think. In days of yore I used to search the same records on microfilm at LDS centre - and that WAS slow with each quarter on multiple reels!!
This is an interesting discussion of problems with the registration system.
http://homepages.paradise.net.nz/mikefost/
This site may have some information that will help in your search
http://www.lancashirebmd.org.uk/
If you check the BDM transcription areas it gives dates as to what has been transcribed. These transcriptions are from the county records - not GRO so will have different reference numbers.
The marriage found by Sally is listed
Lancashire Marriage indexes for the years: 1919
GREENLEES Andrew married CAIN Lena
at Barton-on-Irwell Register Office or Registrar Attended
Register at Salford
Reference BAR/57/182
FreeBDM is progressing and births are almost up to the time of your interest (post 1919) so checking back from time to time could be useful
http://freebmd.rootsweb.com/
This lists what is on the certificates
http://www.familyrecords.gov.uk/topics/bmd.htm
Marriage certificate will have occupation of the groom which may/maynot help your search
Hope this helps
Trish