We did October last year, and thought it was fantastic. Weather was just right (for us); not too hot or humid, but warm enough for water park days. Did
MNSSHP, and that was a highlight for us. Yes, it was a pricey extra, but thoroughly worth it, IMHO.
We did OKW, with the DDP, so almost all food was covered. If memory serves, I think tips were $300ish for the 2 weeks. We had a couple of outside Disney meals, but pretty cheap ones. The only other expense out there was shopping really; we were pretty much pure Disney otherwise, so I think our total spends were <$1500, and could easily have been less without purchase of North Face coats, etc

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I would strongly suggest going on the UK Trip Reports board and finding people who've done that time of year to get an idea about what to expect. I'd humbly point you towards mine (in the sig), except I'm somewhat embarrassed about not finishing off the last couple of days!
We've booked OKW again for October next year. This time with 3 days at Universal. We're lucky in that our kids get a 2 week halfterm, so no worries about absence. Except we're planning to fly Friday-Friday as the Saturday flights are significantly pricier. So still need one day "sick"

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I'd also recommend (closer to the time) touringplans.com. Give great suggestions on good days to do which park, fully taking into account crowds due to parties and F&W. Suggestions worked really well for us. And I'd also recommend the Unofficial Guide book as well. It's a great big thing these days, but it makes great planning material especially as you have a while before you can book.
Have fun planning!