I'm a big fan of B'Twin bikes but I'm not keen on the Ultra 700 but the Ultra 700 AF looks to have been upgraded. I had issue with the cheap chainset but they have since replaced this on the new model with a Shimano non series RS500 setup. When I owned mine I was impressed with the direct mount breaks and the overall handling of the bike. It is value.
Currently they have the Mach 720 at £880 - this is the bike that
Decathlon upgraded me to due to some Ultra 700 issues. If you can afford the extra £130 it is well worth spending the extra - it is a really smooth, comfortable ride and a slightly more aggressive set up (good if you are racing).
I did Ride 100 on my Mach 720 this year and found it a joy.