will soon be getting a specialized crux frameset to build up
the question is what wheels for racing
would I be better going for tubeless tyres and having the ease of being able to change tyres enabling me to use the wheels for both cyclocross racing and also road training with different tyres rather than having two different pairs of wheels.

is the rolling resistance of tubs better than tubeless?

Things to keep in mind: Tyre choice on tubeless CX kinda sucks. Another problem is that many of the easier to set up tyre/rim combos result in a tyre which is too wide for UCI cross rules - something to think about for racing. It works really nicely when set up well though and by that I mean lots of attention needs to be paid to the tyre and rim bead interface, making sure the tyres are sealed correctly (from pinholes etc) so you don't loose pressure while riding which compromises bead retention. It's also a good idea to 'pre-stretch' tyres with a tube too. It's definitely not as 'plug in and play' as tubulars. Often more work than gluing alone, the upsides are that once you've got things set up for your tyre rim combo, you don't really need to keep testing 'bead locks' or anything over and over again. Fixing flats doesn't require a needle and thread - very very very handy if you like to train places where thorns, sticks, rocks and MTB's are more the norm.

Personally I think the rolling resistance is as much an issue to do with correct tread selection in this scenario as it is to do with tubular/tubeless.

One of the key benefits of riding tubulars is that you can run really low pressures without the snakebites of clinchers. With tubeless, the danger is 'burping', which would be a big problem.

I don't think you will be able to use the same wheels for road use and 'cross use (unless you want to wreck your race-day tires). Stripping and re-gluing twice a season would be painful. It would be better to re-build a set of old Ambrosio Synthesis or Montreal Durex rims on new hubs and use those for your road wheels.

Tubular.... Tubeless is not ready for prime time yet. Some folks are having good luck with tubeless but I see and hear of so many problems others are having.

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2 Serotta's, 1 Spectrum, 1 Van Dessel, 1 Parlee & 1 Carl Strong, & 1 Titus.

Hands down tubulars. I steer people away from tubeless setups

cool cheers guys, would be looking for a cheapish reliable tubular wheelset then. waiting for an insurance pay out at the moment so can't afford it now but what sort of options are available up to a max of about £300 probably?

The good stuff is Dugast or FMB but for reliability and durability Tufo is hard to beat. Thread design is all about the conditions you race in. Its all trade-offs, whats good in one condition might be poor in another condition.

Edit: sorry I missed the word "wheelset"

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2 Serotta's, 1 Spectrum, 1 Van Dessel, 1 Parlee & 1 Carl Strong, & 1 Titus.

In the US, either of these sets of wheels:
http://williamscycling.com/cyclocross_tubular.html
http://www.neuvationcycling.com/product169.html and http://www.neuvationcycling.com/product170.html (note that if you sign up for their email list you get a 10% off coupon).

For tires, Tufo Pro Cubus or Challenge Grifo 32 (or Limus if your races are always muddy). The Tufos will be cheaper and more durable, the Challenges will be a bit more supple.

In my opinion that's the way to go for a basic, good value set of all-around 'cross tubulars.

I raced the last 2 seasons on tubeless. I used Fulcrum Racing 1 2-way-fit wheels and Vittoria XG Pro clincher tires. The system worked very well for 24 out of 25 races, and the one where it didn't work was my fault for not checking tire pressure before the race and then burping out. I had races where I would pull a dozen thorns from each tire at the finish line and not lose any pressure. I think a good tubeless set up is much better than clinchers with tubes, even with sealant in the tubes.

However, I think the success of a tubeless setup is very dependent on the tire rim combination. And I have tried several combos that I wouldn't trust for racing.

This year I built a tubular wheel set with HED Belgium rims and glued on a pair of FMB tires and they are way better than the tubeless set up. At the same air pressure, the tubulars ride much smoother and have better traction in corners, and I can run lower pressure in the tubulars than I can in tubeless. The time and hassle of figuring out a good tubeless tire/rim combo and getting tires to seal up is the same or more than the hassle of gluing tubulars.

Tubulars>Tubeless>Clincher