Swift 18 Owners

Could somebody give me a clue, what length of rope to get, to rerig both Halyards, on a Swift 18. I have been to two Chandlers in Lymington, and they both have no idea. Thank you.

On mine, the genoa halyard is 13 metres and the main was 16 metres when cleated to mast, but I replaced with 20 metres so it could be led back to the cockpit & some to spare. Both 8mm braided polyester.