Please do not give Euro or British coins to the locals as a gift or when purchasing goods.
The reason is they cannot exchange them at the banks in Egypt - this can create problems for visitors following in your foot steps. They hassle other tourists to change into Egyptian pounds - this is where people get caught out and short changed especially with 1 Euro coins as they look like 1 Egyptian pound coins. I have witnessed many people getting ripped off and/or confused with the exchange rate and even worse scammed!
The only foreign money I use in Egypt is single US dollar bills for tipping until I get some Egyptian small change. These can be changed without problems.