Mike, my advice is first to try and sell it on forums, and simply ask for sensible offers (to give you a guide), based on what similar kit to yours has sold for recently (anywhere, ebay or whatever), and if you're simply being hit with 'low-ballers', take it to the likes of German ebay (as an auction with a properly assessed fixed reserve), or as Ali says, Gumtree.
Based on my experience, unless you're *very lucky*, the UK is not the market to get a proper price for this type of equipment. Most potential buyers who appreciate what you've got and are willing to pay what it's
properly worth, will live in the likes of Germany, Greece, Italy or the US, or perhaps even Japan.
Therefore, you need to expose your ad to those types of buyers, and be prepared to pack the gear professionally (you've already got a head start here, as it's boxed as new, which trust me will be a HUGE selling point), insure it properly and ship it abroad, as IMO the rewards of doing so, in terms of the price you're likely to get, compared with selling it here on forums, will be more than worth it!
Marco.