abstract: For countably infinite IFSs on the plane consisting of contractions with diagonal linear parts we give conditions under which we can relate the Hausdorff, affinity and lower box-counting dimensions. Moreover, we identify a family of countably infinite IFSs for which the Hausdorff and affinity dimensions are equal and which have full dimension spectrum. The corresponding self-affine sets are related to sets of numbers for which their signed L\"uroth expansions satisfy certain restrictions.