Thanks to Peter MacDonald who has looked at the plaid in both pieces in the photographs and has offered his considered opinion as to the dates and maker of both:

"What a couple of gems you have there. I've sent the link to a friend who's more knowledgeable on the history of kilts (the kilt style appears later than the material) and I'll reply fully once I've heard back from him. What I can tell you at this stage is that the material in both garments is c1800-40, is natural dyes and was woven by the famous weaving firm Wm Wilson & Sons of Bannockburn. The plaid is not a feileadh mor or great kilt as you suggest, it's too short. Rather, it's finished as a separate little or shoulder plaid. The tartan in the plaid is interesting as it appears to have been deliberately woven with brown in place of the usual green and green for black in the Graham."