Even if someone accepts to escrow these coins, I was trying to find their value. The best price that I found on eBay is £450.00 for
1971 2p New Pence Coin and £250.00 for
Rare 1982 Twenty Pencethat's a total of £700.00, or ~$968 (1 USD = 0.72305 GBP today) which is much less collateral than the amount requested.
Even worse: those are asking prices, and obviously nobody has bought them yet. The seller doesn't sell other expensive coins, so I wouldn't take the asking price as their value.