I can't comment on the specific bike options suggested by the OP and others, but I am in the process of getting a CX bike too (for similar intentions as the OP).
I couldn't find the bike I wanted off the peg for <£1K so took the option of specing and building my own. Mostly through careful purchasing of components on sale, cashback deals, selecting the "right" bars, saddle, gear ratios, etc., as well as one eBay purchase (shifters - why are they so expensive) I will soon have the bike I want ... a Kinesis T5 with Pure CX carbon fork and 105 througout for <£950.
You may want to consider the self-spec option too? Not always cheeper, but makes sense if you think you will be changing some components in near future. The Planet X XLS is tempting for £1.3K though.