I have always rated the NAS Spacemat as a general cheap all-rounder and Tom always recommended placing it ON TOP OF the Garrard mat and adjusting VTA accordingly.
Alex, get some rubber rings (specially made for the job) and place them round the periphery of the platter in between the strobe markings and try to get an original mat for completeness anyway. The Garrard mat isn't good for clumsy idiots like me who want to play 10" and 7" discs though - I scratched my nails several times trying to lift them off the platter.
Isn't the Loricraft mat a cork one?
I also suspect that one of Dave Cawley's mats would be an excellent choice too, as the Techie platter rings without proper damping.
Tear down these walls; Cut the ties that held me
Crying out at the top of my voice; Tell me now if you can hear me