Hi Jill,don't know if this is any help, but I do know for a fact that there were Johnston in Co Westmeath as I've got a Bridget Johnston on my family lists.I've typed in a search at IFHF & they have a record of 192 births,95 marriages,50 deaths for Johnston in Co Westmeath.Griffiths Valuation listed 48 names for Johnston in Westmeath & I notice that there are two listed for the parish Newtown Westmeath -Fineas Johnston,tenant of house & garden,townland is Ballykilmore,place name Tyrellspass.Then other one is William Johnston, he is a landlord,townland Ballykilmore & place name is also Ballykilmore.Hope this may give you some leads,Regards Nipy