The coin posted is a Guernsey Crown from 1980, celebrating the Queen Mother's 80th birthday. It is not silver and sadly has little value these days. (face value was 25p at the time, modern Guernsey stuff floods the market and First day covers are out of fashion.)
I don't recommend trying to post them all here as it sounds like there is quite a lot, and much of it will be very common. If you can find a local collector or dealer in your area, they would be able to spot anything worth posting easily. A few guides:
- British bronze coinage of 20th century is mostly scrap metal these days unless it is early and in excellent condition.
- British white metal coinage has silver content if it is dated 1946 or earlier and this boosts the price a lot. post 1947 it is cupro-nickel and is again scrap metal unless in excellent condition.
- Channel Island, Isle of Man etc coins can be interesting if they are early, but the commemoratives post 1970 are low.
- Surprisingly, early 50ps can be good, so check those through.
- Foreign coinage is a much bigger topic, but mostly needs to be pre-1965.
I hope that helps.