Since they aren't 300 years old the probably don't qualify as treasure as that's part of the old act and new revison

http://gouk.about.com/od/tripplanning/a/Finding_Treasure.htm

but depending on where they were found the finder may not have any right to them anyway as generally unless they were deliberartely abandoned (and you could prove it) the original owner (or their heirs) would have the strongest claim

after that the landowner or property owner may well have a stonger claim than the finder

http://www.inbrief.co.uk/land-law/objects-found-on-land.htm

I'd suggest contacting https://finds.org.uk/ first (even though I susepct it's not treasure) as this will eliminate any change of fines or prison sentences if i'm wrong, and they may be able to provide you with advise over what to do next