ACROSS
1 cath, 3 dehen, 6 pellwolok, 7 pel, 8 nawves, 10 keus, 13 coref, 14 gwandra, 17 to, 18 te, 19 sagh, 20 yagh
DOWN
1 cresyk, 2 gwely, 4 qwylkyn, 5 oll, 7 pentir, 9 sqwith, 11 scath, 12 hesken, 15 drog, 16 gwary
Note that the first and second editions of the Skeul an Tavas coursebook wrongly spell pentir 'headland' as pedntir. The stress is on the second syllable, so there is no pre-occluson in the first part of the word.