My wife and I have been resident in Andorra for 15 years and wish to
divorce. Andorra is my domicile of choice but my wife's domicile
remains the UK. We have both been considered "not res not normally
res" during this time. We have no address in the UK and have not lived
there since 1987. To the best of my knowledge the UK courts do not
have jurisdiction unless my wife returns to the UK to live (for one
year?) and the Andorra courts do not have jurisdiction as we are UK
citizens. My question is a/ if we obtain a divorce in one of the
offshore locations such as DR, Haiti, Guam etc. will the divorce be
recognised in the UK. Is there a law firm or specialist - preferably
with a web site - that can help us and b/ is it correct that the UK
courts do not have juridiction in this case.

You may want to simply contact your closest British Consulate General.
They are well-informed on such matters of international law. In the
past they have helped me (a UK citizen) with all matters concerning
marrying a US citizen in Germany and with matters concerning our
dual-national children. They will be able to tell you what is required
under British law. It has been my experience - in Germany - that
international papers can be drawn up. Our German marriage license is
an international document and has been accepted without issue in both
the UK and US when applying for our children's respective
citizenships. I believe that one requirement may be to post notice of
divorce at the consualte for a given period in order to meet British
law - as was my experience with getting a marriage license.
Furthermore, you can also charge your divorce attorney with the
responsibility of researching and meeting the requirements of British
law.
I don't believe it's a case of jurisdiction but of simply meeting
certain criteria in order for your divorce to be recognized where you
need it to be recognized.