I can confirm that pro3 doesn't work for campag in 11v. It doesn't work for some frames in 10v either. The spacing / cassette carrier body has not been designed / spaced to suit.
Given the obviousness of this problem & the fact its not been rectified by hope, it kinda tells you something about how much they care about the road market imo.
The 240s rear hub is not the most ideal as its spacing is not optimum for campag either. I've always found it a little soft in the rear compared with a record hub based build.
The design and bearing quality of the 240s is very good though, so if your not too heavy (> 70kg?) or honking out the saddle all the time you might not notice it. I do like the fact you can change between the carrier splines on 240s as well, which is a nice feature if carrying the hubs as spares with other riders. I do keep being tempted by the 370s version as frightening as the weight is, as it would be a very solid but economic bit of training kit.
For a nice price build with reasonable weight, consider record hubs from ribble (£160ish) + open pros (£90ish). I don't personally think the ceramic version is worth the extra really, unless you prefer a nice clean look. Its £100 extra on the rims and will either have flaws (the famous manufacturing defects) or get a dink in (life being as it is
Open sport is not that much of weight penalty @ 50g for a much better price and it begins to allow you to think of the rims as properly disposable, even though they are as solid (more solid perhaps) than the std open pro rim. IMO its got a nice no nonsense look about it. The brake surface is really good.
I run a lot of different wheels and honestly prefer the speed of the traditional bearings in campag wheels over anything else. Training wheels and weights as long as they are around > 1600g should make things all pretty similar. You certainly won't notice the difference between a 20mm rim and a 30mm rim imo. A decent set of tires will make a much more noticeable difference.
Training wheels should be solid, reliable & leave plenty of space in your budget if done right for buying better kit or race wheels for when it all counts.