The best way for me to get to CC from HH, according to Travel Cymru, is a train to Landidno?, then bus that takes me to CC.
I can't check times yet as it does not go that far in advance yet.
I'll get there, even if I have to hitch. 
Re kit. Temps. on hills could be well below zero, or not much above that time of year.
I'd take a set of heavyweight baselayers and a set of midweight ones. That should cover you, take a close fitting midweight fleece, (heavy, if you run 'cold'). Waterproof Jacket and Trousers.
Boot wise, 3 season boots would be recommended.
If you haven't used or got skills to use crampons and axe, I'm sure there will be lower routes where you don't need them.