Need to send a few pairs of snowboard pants back that don’t fit – weight is <4kg and it’s a small parcel but the value is about £650. Was gonna send it via collectplus or similar but they won’t cover that value and only couriers that will provide that level of insurance want about £25, which makes the pair of pants I’m keeping very far from a bargain!

Any suggestions? 🙁

The post office.
either Royal mail special delivery, with insurance to £500 included, or parcelforce,with variable cover rates.
Or Interparcel?
Insurance is going to cost you! £25 aint a bad deal for a 4kg parcel.