HMRC draw the line at £15, officially anything over that is liable for VAT, if it goes over £135 its VAT plus import duty
the chinese know all this and very rarely will they declare the value over this. we buy a lot of stuff from china and almost always it gets declared as $10 regardless. granted its all small packages (smaller than a shoebox) and even if it comes via DHL rather than airmail its almost always got 'gift' and $10 on the customs declaration. HMRC aren't daft though. I've laso bought electronic from the states, VHF radios/radar modules/chartplotters. with these its pretty much 50/50 wether they want duty paying. if they look cloely at the contents you get a bill.
anything we get in big boxes, always comes with a bill for duty.
any road... just order one of them things off ebay, will see what the crack is when it arrives.
http://aliexpress.com often cheaper. they also hold the funds in escrow till you have received the goods and are happy with them before releasing them to the seller. the few disputes I've had over wrong items have resulted in either being offered a 50% refund and keep the goods, or the seller has said keep them anyway and sent the correct ones. as yet haven't had to ship anything back