It's always been a carp/coarse fishery with good fish in. I've only coarse fished it and did a stint of work experience and help working for boyer leisure who owned it working with Tristan the baliff at the time. That was some 17 years a go. The lake is split up and has loads of bays and areas. It's a fair old walk round but I would think spending time to find them in that kind of water will play a significant part.
You also have Thorney Weir on your door step and parts of the Colne round there due to flooding hold good carp.
It's a shame I moved to Shropshire as the waters near Ruilsip where I'm from have some cracking fish in them.