I used the same e-bay seller you linked, carbonwheels2011. I bought the 50mm Tubular Link Here
I ordered them on 28th Feb, were drilled up to my specs and shipped on 4th March and arrived in the UK on the 13th, it then took 2 days to get them to the Channel Islands from the UK.
I was originally going to use Tufo Tape for ease of use but after reading up I think I'm going to glue them as it's stronger and recommended if you're going to be racing with aggressive cornering.
I love how loud the rear hub is, it will probably be even louder when mounted to the bike!
Coming in well under the quoted weight range then, bonus!

And rapid delivery from across the other side of the planet!

Think it might be wise i go for a cheaper set and then weigh up whether i like tubs or not then upgrade in future or see how the tech develops.
38mm would do me fine as they are lighter and will be less susceptible to side winds than 50mm plus weigh a bit less though less aero benefit.
I'll keep my alloy clinchers anyway so can revert back quickly.
Mostly read good things about the Tufo tape, people who have used it for years with no problems. I guess as you say for crits and the like it would be best going for glue, mine will be purely used for general road riding.
What tyres and brake blocks are you going to use?