I think the Zap-a-Gap range of superglues, designed with hobbyists in mind, includes not only a debonder but also an accelerant. But I don't think this range is available in the UK yet.
As far as stripping miniatures goes, I've tried a lot of products over the years. For metal miniatures, by far the most satisfactory to use has been Blackfriar's Paint & Varnish Remover. Don't get it on plastic! It also makes superglue and greenstuff easy to break off, but has no discernible effect on Milliput.
R.