I dont mean to confuse you here, but I wear size 8uk sports & dress shoes.
But I purchased a pair of 8.5uk of adidas weightlifting shoes and they fit just fine. Id also heard about the "order a size smaller" thing so was worried, but they fit perfect.
Id recommend you buy the same size as you have for your chucks. I think its better to have fractionally loose, than so tight it hurts.