But double white lines and variants are diagram 1013.1, and hence are not covered by this rule. I think paragraph 3(a) and 4 combine to give info on double-white lines. The relevant snippet is this one.
"(3) Subject to paragraph (4), studs incorporating reflectors or retroreflecting material and so spaced as to form a single line of studs not less than 3 nor more than 4.5 metres apart shall be fitted -
(a) between the two lines consbreastuting the marking shown in diagram 1013.1, except where that marking is so placed that the continuous lines shown in version B of diagram 1013.1 are more than 175 millimetres apart and are separated by an area of cross-hatching so shown;
(4) Where the marking shown in diagram 1013.1 is placed as mentioned in the exception to paragraph (3)(a), the studs mentioned in paragraph (3) shall be fitted either in opposite pairs within the width of each of the two lines or in a single line between those lines."
(3)3(a) clearly applies as the OP mentions hatching - so clearly likely to be more than 175 mm apart.
4 describes what to do in the case that 3(a) applies. The cat's eyes could be placed in a single line - like if the double white-lines were as normal with no hatching. The other option, as I read it, says that studs should be placed on each of the lines if two lines of cat's eyes are chosen and 3(a) applies.
So looks like, provided that I've read and interpreted (4) correctly, that studs on the lines are fine if (3)(a) applies.
