The only Robinette I can see on Brian Lawson's burial index is ROBINETTE, Emily [age] 68 Bra[ddan] 2 Apr 1936.

If she was related perhaps William Francis was buried in Braddan more recently than the dates the index covers?
You didn't give a date. His death cert would give the address of where he was living.
www.gov.im/registries/general/civilregistry/ [see "Contacts" top of page].

There was RABENECK, Eileen Norah 43 Mau 20 Aug 1938 [buried in Maughold] which could have been misspelt.

Sue