Home Guard Records are still with the Ministry of Defence, the only exception being those from the Durham area which have been digitalised as a pilot study and are available from the National Archives. I believe it was the intention to release all the records in this way eventually, but apparently they have run into a snag with data protection, a substantial number or records relate to men still living who served as youngsters.
You are right in your supposition that they don't reveal very much, name, rank, next of kin, address and unit, dates of enlistment etc. are just about it on the examples I've seen.
jds1949