HI mate i had the 666 which just has longer legs, to fold the quad you need to loosen the back bolts , and then to fly re-tighten again which can be a pain , the parts are not to bad to get hold of. The 666 has not parts in UK unless you use the 525 parts that are used on both , i was un-lucky with mine you can see it in my profile pic, one motor had power fail and quad fell from 200 feet it landed into the grass and soft ground , but it still snapped 3 motor mounts clean off its arms ,one arm snapped , and all pins on FCB bent, there is no room between the top and bottom plate to fit much , I have PCB in there and thats all that it will take , even tho this happened I was still happy with it , you will have a hard time mounting a go pro as there is no room to fit mount , The 666 and 525 are just fun flying quad like a large acro quad , it can be done but will be a massive pain to fit, if it was me I would go for a 450 dead cat frame or a clone of the hoverthing FPV flip frame , or TBS Discovery frame , some frames are made really for FPV they are more stable have better places to mount the go pro , and the props will not get into camera shot the frame will be cheaper if you buy as a kit like from Hobby King even the x525 is very cheap from uk warehouse , there is a H frame on there site which would make a nicer camera frame has legs that fold but still bolts to mess about with but is not as big if left as an H , and get motors ,ESC ,FCB, everything really from HK and not have to rob a bank , if you want top end frame etc a really good frame like the TDS Discovery frame will be about £165 just for the frame , also the if your going to have the go pro as the FPV camera it works on 2.4g the same as the transmitter ,this is why blade 350qx has control problems if you use the go pro , i am in luton so not a million miles away and am always willing to help , once you know what frame you want (cheap) go for H frame take a look on HK get the weight and weight of go pro and mount then go on ecalc put in the quad weight as the frame and go pro with mount and tell it without drive , it will then as you add parts work out total weight and will work out flight times , mess about with battery 3 cell/ 4 cell min i would go would be 4000/ 5000mah and props size and pitch and see what this does to your flight time , low kv motors with big props gives better flight times with a good battery here is the link sorry post was long but your need to get it right or your just waste money
http://www.ecalc.ch/xcoptercalc.htm?ecalc&lang=en
