honest answer,
You can DIY for less than a tenner from amazon.
the replacement glass back just needs to be removed using heat then clean with alcohol based wipes cue tips /nail varnish remover. insure the contact area of the device is clean and dry before you apply the new back cover. Covers are up on sale for less than 10 pounds from amazon and you can replace it with the color of choice etc. as it won't revoke your warranty to replace it yourself as long as none of the Electronics are removed or seals on them broke (the battery has a a seal on the bottom right you should avoid pulling that tab.