Hi Neil,
I don't want to rain on your parade, but don't hold your breath. DX clubs tend to rather different animals than your average general interest ham club. Rightly or wrongly, they are pretty exclusive places to hang out. I scanned the TDXS member roster and saw the calls of some pretty heavy hitters in the DX/contesting world. There's less than 160 members in the entire club, probably all of which have worked 300 countries and the majority of whom will be on the honor roll. These guys are ALL 20 WPM Extras and I don't see ANY N5 calls with three letter suffixes. These groups tend to select members on the basis of what they feel the nominee can bring to their club, rather than on the basis of the new member's desire to learn. Snobbery? Perhaps, but if you want to join their club, I would suggest you get busy, work a bunch (like a WHOLE bunch) of DX, get on the honor roll and get your 5BDXCC. Kick a few of their member's butts in some pileups and contests, that'll get their attention. When members start to recognize your call as a player in the DX world, the doors will begin to open. Sound like a tall order? It is. You gotta pay your dues if you wanna hang with the big dogs.
Hey, don't shoot the messenger...
Good Luck