In reply to Sam Edwards: haha! There's no times to avoid as its really quiet these days. 10 yrs ago Marple would be heaving most week nights as it was the only larger wall in Greater Manchester, we used to drive out to Warrington as well. Nowadays it's still pretty good and quite extensive. They use old style holds which I find quite tweaky. Lovely friendly people who run it as mentioned. Lunchtime bouldering deal is good value. Other times I think it is q expensive.
Awesome walls is only 20 mins drive away and is quite frankly in a different league.
More importantly Marple is half an hour from the Roaches cheedale or Raven Tor, 5 mins to new mills, 20mins to Windgather or castle naze etc etc. so no real need to worry about walls