Dan,
Re: Mackeral for cod - don't bother - squid is the bait to use. Mackeral strips will get you whiting though.
( If you havent got any squid I can do you a block for a reasonable price if you want to collect before Tuesday. )
Personally, if I were going out and couldn't afford to get to the needles, I would choose the gulley just off the ledge ( got 2 cod last year from around there ). Double Squid on a pennel rig doing the trick.
Alun J is "the man" to advise on best locations there.
Also, if fishing whole squid there is always the chance of a good bass.