I dug out the booklet I mentioned and I'm afraid there is no joy there. Mike Brown's parish register transcriptions start in 1770. The text is very dense and I had a skip through but nothing stood out. So probably not worth pursuing that direction - although Deborah O'Brien, who can often be found on the DEVON FHS message board (
http://members.boardhost.com/devonfhs/) is very knowledgeable about that particular area of Devon and might be able to help.
From my own experiences researching family history I would guess they are probably related somehow - I've found loads of cousins and second cousins marrying - but at that early date it will be difficult to prove as these trades/crafts families do move about so. I've also found almost as many older women marrying younger men as vice versa (especially second marriages). And a last observation: there were loads and loads of masons and builders in the Horrabridge area (was it the availability of the local granite I wonder?) and my lot moved on out to Exeter (St. Sidwells) and then on to the coast to take advantage of the building booms there in the early to middle nineteenth century. Various sons and family members took up different branches of the building trade, e.g. slaters, plumbers, glaziers, etc.
Good luck!
Sandra