Wish I could help you find the castle pattern. I have mine 1/2 done. I can't work on it exclusively. I must work on it for a couple of weeks, then put it away for awhile.
I did NOT change the cloth for the castle, but after I was 1/4 of the way done I had wished I had. I am not a big Aida fan. I like the look and feel of evenweaves or linen. Plus it makes 1/4 stitches so much easier than poking through that tough Aida. Personally, if I had to start it over again, I'd switch to an evenweave or a linen in the same basic color.
I learned my lesson though. Just finished a Suzy Zoo cross stitch for my neighbor's new baby and I switched that to a 28 ct fabric instead of the 14 ct Aida that the kit provided.
If you're used to linens or evenweaves, then it won't be too hard to switch.
HTH