First up, don’t let them expire! Buying, spending or sharing any amount of avios resets the clock on *all* of them for another 3 years. Other than flights, you can convert them to Nectar points. Lots of flight options though. Have a look here for ideas headforpoints is a superb resource. https://www.headforpoints.com/category/avios-redemption-university/

I bought a case of wine with mine. https://thewineflyer.co.uk