Thanks for the advice everyone.

Sorry but I saw your posting too late Bret.  I went down the chemical route to solve the problem.  I did try sanding with a grit as low as 60 but it just made a worse mess.  In the end I tried the following (test patches)

Oomph glue solvent - very slow and not very effective
gum turpentine - no effect
shellac - little effect
metholated spririts - some effect but slow
white spirit - little effect
paint thinners - messy but softened glue quickly

so I settled on using thinners and a paint scraper as well as grade OO wire wool.  The end result looks very good and the wood now sands normally.

I'll be washing the cab down with sugar soap, then sanding and will wait a week before sealing with a water based floor varnish.  Hopefully the decals will stay on ok!