Quote:
Am I on the right lines? All hints accepted...


Yes, you're on the right lines:

Spoiler:
Lbh trg gur ebpxrg ynhapure gb uvg TYnQBF (ol bcravat na rkvg ng gur hccre yriry, naq na ragenapr ng gur ybjre yriry -- fgnaq va sebag bs gur ragenapr naq gura qbqtr), naq na beo snyyf bss. Lbh gura chg vg va gur sheanpr. Lbh unir gb ercrng guvf sbe rnpu bs frireny beof.
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-- roger