In reply to lmvt:
check out this link for grades.
http://www.alpinist.com/grades/
as for bolted routes there are some in the slate quarries of llanberis but most require a trad rack to be carried as well.
i think there is some bolted stuff on the north coast not sure where though.
the slate routes could be top roped i think though i have never tried it myself.
enjoy (just dont get your bolt gun out down the pass you could get lynched)