+1 what Wally said. I've been mooching guild dungeon access from BS for a long long time. Hopefully one day i can WOE more for them, so what i do is pay taxes to BS...
i've heard some ppl pay money for guild access for X amount of time too...
so perhaps you could work out a deal with WOE castle holders?
and imho what Panda is slightly suggesting isn't bad at all. Similar to the deal making i suggested above, yet somewhat more like an open tender... xP