I got a 6d for £1149 from HDEW. Plenty of posts on here of how reputable they are etc if you need to research them before you spend with them. 3 years warranty - 1 year with them (Using a UK canon dealer) and the other 2 years are some insurance warranty they give. I rang them first and asked questions and they were very helpful. The camera was posted from Hong kong so make of ot what you will. I paid by credit card though so no "Bank transfer only" risk.
I bought a 5D MkII off here 2nd hand and sold it on to fund the 6D (Price difference wasnt much so took the risk). The prices weirdly went up for 2nd hand - i either got a bargain or the 2nd hand market for 5DMk2's improved (Initial jumps to the Mk3 settled?)
All depends on what YOU prefer out of a camera and what you shoot. Mk2 is excellent, many people have made good livings using it, but i just never clicked with it (pardon the pun), much much prefer the 6D - in terms of weight, features etc.
GPS i couldnt care less. Low light its superb - ISO capabilities are outstanding. AF isnt much in it - slightly better on the 6D for me but i dont take sports/wildlife shots but between these 2 cameras neither would be the better option for that. WiFi is good for me - getting shots of me with the family and generally playing around/experimenting.
Might have just been my copy of the MK2 but i found exposure to be hit and miss - this could also be me at fault and that the 6D is more intuitive ? The 6D exposes shots much much better though for me.
I prefer the general feel, shutter action, dare i say it even button layout of the 6D too. Then i jumped from a 550d to 5DMk2 and then quickly onto the 6D so maybe it was always going to be a better fit.
There are a few 6d vs 5d MkII videos on youtube that should help make your mind up. I found a lot of forums/opinions which end in a 6D bashing because its not a 5DMK3 at £800-1000 dearer. Take them with a pinch of salt. A lot of people disregard anything because it "Doesnt feel pro enough" or its not the best of the best. A lot of people will make the decision because for their requirements or professional needs they need faster AF, dual cards etc
Basically, it depends what you use it for and which suits you best (and your budget).
If you can get anywhere and try them both first then that would be my best advise
