A 29er wheel might struggle with fitting cx tyres, certainly crests do.
Do you have any old mtb wheels you aren’t using and could get the hubs rebuilt with some suitable rims?
Other than that the Kinesis set at £250 is pretty good for the money and the latest version is pretty light at somewhere around 1500g, so will help the charge feel more fun.
I built up a croix de fer with 1610g wheels and it is about 22.5lbs with some 105 kit and light pedals, but my mate has a stock one with heavy wheels and the difference is huge, his is a heavy lump and he was very ‘meh’ about it when his fitness was lower than its usual top-notchedness.