Declare it as a RIF if its a RIF when you post it, Parcelforce 48 are fine with carrying them (though Post Office staff don't always know this), make sure its tracked & insured, something like a UMP will be around £12 -15, best to put your and their UKARA nos on in the to/from addresses, but (especially if it involves airmail at any point) DON'T send batteries with it as they are basically banned by PF unless new in original packaging, or gas mags for same reason (anything that is or CAN BE pressurized). If you want to risk sending a battery post it in a jiffy envelope or small box seperately (at least if it doesn't get there its better than having the rif destroyed).