For Wales there are two obvious candidates, OFD & fan gyhirych (725m), DYO & fan brycheiniog (802m), which would make a stunning walk. Darren, Aggie and draenan are all on a much smaller plateau - although you could do one (all 3 !) on way to pen y fan / corn du / Craig Gwaun Taf (886/873/826m), but they are well away from the caves. Little neath & fan nedd (663m) would be the other option (ignoring Tunnel as part of DYO system), or extend that to the 3 highest summits - nowhere near as clear cut as Yorkshire