They seem to be owned by the same people - Tartanweb:

Scottish Kilts
Tartanweb Scotland Ltd.
45 Grovepark Street
Maryhill
Glasgow
G20 7NZ
Telephone: +44 141 333 9136

Irish Kilts
TartanWeb Scotland Ltd.
45 Grove Park Street
Glasgow
G20 7NZ
Telephone: +44 141 333 9136

Regards

Chas