I'd like to get them before they get to eBay. I do not recommend buying uncleaned coins. Rest assured you are competing with many other people with the same idea.
Finders usually deal with nearby dealers in Europe or the Middle East first.
Then the coins sometimes come to major U.S. coin shows to be sold to U.S. dealers. Some buyers travel regularly to shows in England and Europe. I have been to minor shows in England where detectorists had thousands of terrible coins for sale. Over time, you could build up a relationship with a local and have him ship you material. There is a lot of trust built up over time between wholesalers and dealers.