Buchanan family - Walter /John c 1700s

[Bridgebabe]

Struggling to find family of Walter Buchanan prob born abt 1725. He married in Penrith 1754 and died 26 May 1770 Penrith.  I have found details of his children from census etc (but not their baptisms)  Two of his sons went into RN as officers and I wonder if Walter was naval also.  Would be very grateful if anyone has any 'pointers' to Walter and his parentage (father perhaps John?)
His granddaughter Mary returned to Moffat in Dumfriesshire where she died in 1852, although lived in Penrith.
Any help /ideas much appreciated    - thank you