They have HORRENDOUS reviews!
https://www.trustpilot.co.uk/review/phones.co.uk
By bad customer support means they claim phone is in stock and then you get emailed saying out of stock and it's then impossible to actually get hold of anyone, you don't know how long you have to wait and can't speak to anyone to cancel the order.
Once you have the phone then everything is through the network, however any problems receiving the phone you have to deal with them. Great deal if you receive the phone without any problems, but people have had terrible problems when phone hasn't been delivered