I have a 1500 record Access 2000 database with some 1500 entries and would like to convert it BibTex format, hours of Googling has gotten me nowhere except for converting FROM BibTex the opposite of what I want. Copying and pasting a field at a time is tedious.

If I export to csv it truncates the abstracts  so I presume that there is some other way of getting the data out?

Also to do that effectively I need the file structure and cannot find that described anywhere on this site?

Can anyone offer a suggestion please?

Sounds like you are doing fine.  Did you find the file format for bibtex files?  if not they should look like this:

for each reference:

@reftype{refId,
  field1      = "value1",
  field2      = "value",
  etc...
  }

multiple authors should be split by and:
e.g.
"G. B. Johnson and W. W. Howells and A. N. Other",

It is as well here was no conversion facility as my 10 year old original was very poorly researched. I am now rewriting the whole lot and buiding the bibtex format in a text doc and pasting the strings singly or in groups going into the same category. With good result.