Hi Kidvicious
when did you send the parcels?
The 15 days is the minimum amount of time before Royal Mail will accept that a letter or parcel is lost, and you can then claim (As long as you kept the proof of postage).
The downside to your situation, is that you will end up getting penalized by Swapitshop, with a -3 for each lost parcel
Over the last 5 years, I have had quite a few packages go astray on their way to Swapitshop.
You could always get in touch with SS, to see if they will levy the penalty, although I am doubtful, but you never know.
The only bit of good news is that you will receive a cheque off Royal Mail, up to the value of £28 per parcel (you will have to state what was in the parcel, what the parcel looked like, etc in your claim.)
You have my sympathies, and I hope it works out OK for you.