Just phoned GlaxoSmithKlein who own the Horlicks brand. Horlicks sweets are not available here in the UK and there are no plans to reintroduce them. However they are available in Malaysia under the name Maltese or Maltease not sure of spelling and it was suggested that they may be available in any Malay ex pat shops in the UK.
So if anyone knows any Malaysians, then I'll have some.