The British postal service is not as professional as we would all like it to be. So far this year I have had refunded two items which arrived broken, one which never arrived, one that never reached me and one that after 69 days missing was returned to me as undelivered.
Here are some ideas that I use
Try sellotaping a "going to--comming from" note to the item before wrapping and write "return address enclosed" on the outer wrapping. Then if your item parts company with its wrapping it should either reach its destination or be returned to you.
Check to make sure your pen is waterproof before writing the address, try printing out the name and address and sellotaping it to the parcel.
Write FRAGILE on all sides of your parcel not just the top.
For small fragile items try gravy tubs, ice cream or spread etc plastic containers. Shredded paper makes great additional stuffing, bubble wrap can be picked up free at the supermarket (look in the fruit and veg)
The less room an item has to move in its wrapping the less risk of breakage.
Always get and keep proof of postage at the Post Office, without it you cannot make a claim.
Don't let the Royal Mail get away with loosing/breaking an item always make a claim.
Its always worth remembering that you cannot claim back the postage if an item is returned to you (even if its been carefully wrapped and addressed with a return address and its been lost for 69 days!!!) Apparently its not viable for Royal Mail to do this, so they take our money fail to deliver but keep the costs anyway.