Maybe try chemical reagents first as they can narrow down the identification possibilities - Frank Dobson's 'Lichens' gives details of which apply (or don't) to each species.
The link below is to the British Lichen Society's page giving more details on reagents:
The British Lichen Society - Chemicals for Lichen Identification
and there is also a thread by poschaivious about chemical reagents somewhere in the Lichen section.
But ...... as I've just discovered in the 'Cladonia' thread there is the risk that even thin bleach (C) can include additional chemicals that can make results misleading ........