Hi, i have an issue with getting two courses of block work to line up were one external wall turns and meets a second wall. Can I use 100mm dolly blocks underground below DPC ? 

Yes you can Any of the concrete coursing blocks are fine Most are 7N

Dolly blocks seemed to be an option but it appears that no one in the East of the country can supply them, its a West country thing for hills not a very flat Suffolk. So two more options again still for below DPC sitting directly on top of concrete foundations. Attached is a picture where I have just placed the blocks to show what I am suggesting. Can I move the base block that is laid on its side over to the left and then build flush on one side with an overhang on the other side or can  I cut the base block and then build flush to both sides to leave a 150mm cavity. This is all down to needing space on the foundation for a suspended concrete floor that was not allowed for when initially laying out.