I am going from Oct. 28 - Nov. 4. There is lots to do at WDW at this "spooky" time of year! This should be quite an experience for you, as I am under the impression that halloween is not as big of a "holidy" in the UK as it is here in the US.
There are the haunted hayrides at Fort Wilderness.
Mickey's Not So Scarey Halloween Party (is sold out for Oct. 31st though)
Ther are other events going on at various resorts on Oct. 31 for the kids.
I am sure there will be some special stuff going on at Pleasure Island on Halloween for adults!
Check the DISboards sister site,
www.wdwinfo.com for more information! have a great trip!