In Cost Conscious Cruiser, published 1999, Lin & Larry Pardey list a Danish and a UK insurer as possibliities:

International Health Insurance Danmark A/C
8 Delagegade
1261 Copenhagen, Denmark
Tel: 45-3315-3099, Fax: 45-3332-2560

Health Care Group - Private Patient Plan
International Insurance Dept
Phillips House, Crescent Road
Tonbridge, Kent, TN1 1BJ, UK
Tel: 44-1892-512345, Fax: 44-1892-51514

We haven't tried them yet, but may need to do so this year. Has anyone had experience with either of these?

Alan