what to do with british coins?

I recently went on holidays to Scotland and have a good few coins let over but I thought my local credit union would exchange but they wont. Any ideas what I could do with these coins? Is it true I could pay for stuff in tescos with sterling? I have about €30 in coins

Save them for the next trip to the UK.

Shops here will not accept them and certainly Tesco will not accept them.

Cross border shopping?

sainsburys in newry now has one of those lovely machines at the door that takes your coins. i have looked at it but could not see the rate of commission charged.
if you do visit newry sainsburys, save some of the coins for parking - new system is now in operation and the queue to pay for parking is crazy.